Ideal gas

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Ideal_gas

An ideal gas is a theoretical gas composed of many randomly moving point particles that are not subject to interparticle interactions. The ideal gas concept is useful because it obeys the ideal gas law, a simplified equation of state, and is amenable to analysis under statistical mechanics. The requirement of zero interaction can often be relaxed if, for example, the interaction is perfectly elastic or regarded as point-like collisions.

Under various conditions of temperature and pressure, many real gases behave qualitatively like an ideal gas where the gas molecules (or atoms for monatomic gas) play the role of the ideal particles. Many gases such as nitrogen, oxygen, hydrogen, noble gases, some heavier gases like carbon dioxide and mixtures such as air, can be treated as ideal gases within reasonable tolerances over a considerable parameter range around standard temperature and pressure. Generally, a gas behaves more like an ideal gas at higher temperature and lower pressure, as the potential energy due to intermolecular forces becomes less significant compared with the particles' kinetic energy, and the size of the molecules becomes less significant compared to the empty space between them. One mole of an ideal gas has a volume of 22.710 954 64... litres (exact value based on 2019 redefinition of the SI base units) at standard temperature and pressure (a temperature of 273.15 K and an absolute pressure of exactly 10⁵ Pa).

The ideal gas model tends to fail at lower temperatures or higher pressures, when intermolecular forces and molecular size becomes important. It also fails for most heavy gases, such as many refrigerants, and for gases with strong intermolecular forces, notably water vapor. At high pressures, the volume of a real gas is often considerably larger than that of an ideal gas. At low temperatures, the pressure of a real gas is often considerably less than that of an ideal gas. At some point of low temperature and high pressure, real gases undergo a phase transition, such as to a liquid or a solid. The model of an ideal gas, however, does not describe or allow phase transitions. These must be modeled by more complex equations of state. The deviation from the ideal gas behavior can be described by a dimensionless quantity, the compressibility factor, Z.

The ideal gas model has been explored in both the Newtonian dynamics (as in "kinetic theory") and in quantum mechanics (as a "gas in a box"). The ideal gas model has also been used to model the behavior of electrons in a metal (in the Drude model and the free electron model), and it is one of the most important models in statistical mechanics.

If the pressure of an ideal gas is reduced in a throttling process the temperature of the gas does not change. (If the pressure of a real gas is reduced in a throttling process, its temperature either falls or rises, depending on whether its Joule–Thomson coefficient is positive or negative.)

Types of ideal gas

There are three basic classes of ideal gas:

• the classical or Maxwell–Boltzmann ideal gas,
• the ideal quantum Bose gas, composed of bosons, and
• the ideal quantum Fermi gas, composed of fermions.

The classical ideal gas can be separated into two types: The classical thermodynamic ideal gas and the ideal quantum Boltzmann gas. Both are essentially the same, except that the classical thermodynamic ideal gas is based on classical statistical mechanics, and certain thermodynamic parameters such as the entropy are only specified to within an undetermined additive constant. The ideal quantum Boltzmann gas overcomes this limitation by taking the limit of the quantum Bose gas and quantum Fermi gas in the limit of high temperature to specify these additive constants. The behavior of a quantum Boltzmann gas is the same as that of a classical ideal gas except for the specification of these constants. The results of the quantum Boltzmann gas are used in a number of cases including the Sackur–Tetrode equation for the entropy of an ideal gas and the Saha ionization equation for a weakly ionized plasma.

Classical thermodynamic ideal gas

The classical thermodynamic properties of an ideal gas can be described by two equations of state:

Ideal gas law

Relationships between Boyle's, Charles's, Gay-Lussac's, Avogadro's, combined and ideal gas laws, with the Boltzmann constant k_B = R/N_A = n R/N  (in each law, properties circled are variable and properties not circled are held constant)

Main article: Ideal gas law

The ideal gas law is the equation of state for an ideal gas, given by:

$${\displaystyle PV=nRT}$$

where

• P is the pressure
• V is the volume
• n is the amount of substance of the gas (in moles)
• T is the absolute temperature
• R is the gas constant, which must be expressed in units consistent with those chosen for pressure, volume and temperature. For example, in SI units R = 8.3145 J⋅K⁻¹⋅mol⁻¹ when pressure is expressed in Pascals, volume in cubic meters, and absolute temperature in Kelvin.

The ideal gas law is an extension of experimentally discovered gas laws. It can also be derived from microscopic considerations.

Real fluids at low density and high temperature approximate the behavior of a classical ideal gas. However, at lower temperatures or a higher density, a real fluid deviates strongly from the behavior of an ideal gas, particularly as it condenses from a gas into a liquid or as it deposits from a gas into a solid. This deviation is expressed as a compressibility factor.

This equation is derived from

• Boyle's law: ${\displaystyle V\propto \frac{1}{P}}$;
• Charles's law: ${\displaystyle V\propto T}$;
• Avogadro's law: ${\displaystyle V\propto n}$.

After combining three laws we get

${\displaystyle V\propto \frac{nT}{P}}$

That is:

${\displaystyle V=R\left(\frac{nT}{P}\right)}$

${\displaystyle PV=nRT}$.

Internal energy

The other equation of state of an ideal gas must express Joule's second law, that the internal energy of a fixed mass of ideal gas is a function only of its temperature, with ${\displaystyle U=U(n,T)}$. For the present purposes it is convenient to postulate an exemplary version of this law by writing:

${\displaystyle U={\hat{c}}_{V}nRT}$

where

• U is the internal energy
• ĉ_V is the dimensionless specific heat capacity at constant volume, approximately 3/2 for a monatomic gas, 5/2 for diatomic gas, and 3 for non-linear molecules if we treat translations and rotations classically and ignore quantum vibrational contribution and electronic excitation. These formulas arise from application of the classical equipartition theorem to the translational and rotational degrees of freedom. 

That U for an ideal gas depends only on temperature is a consequence of the ideal gas law, although in the general case ĉ_V depends on temperature and an integral is needed to compute U.

Microscopic model

In order to switch from macroscopic quantities (left hand side of the following equation) to microscopic ones (right hand side), we use

${\displaystyle nR=N{k}_{\mathrm{B}}}$

where

• ${\displaystyle N}$ is the number of gas particles
• ${\displaystyle k_{\mathrm{B}}}$ is the Boltzmann constant (1.381×10⁻²³ J·K⁻¹).

The probability distribution of particles by velocity or energy is given by the Maxwell speed distribution.

The ideal gas model depends on the following assumptions:

• The molecules of the gas are indistinguishable, small, hard spheres
• All collisions are elastic and all motion is frictionless (no energy loss in motion or collision)
• Newton's laws apply
• The average distance between molecules is much larger than the size of the molecules
• The molecules are constantly moving in random directions with a distribution of speeds
• There are no attractive or repulsive forces between the molecules apart from those that determine their point-like collisions
• The only forces between the gas molecules and the surroundings are those that determine the point-like collisions of the molecules with the walls
• In the simplest case, there are no long-range forces between the molecules of the gas and the surroundings.

The assumption of spherical particles is necessary so that there are no rotational modes allowed, unlike in a diatomic gas. The following three assumptions are very related: molecules are hard, collisions are elastic, and there are no inter-molecular forces. The assumption that the space between particles is much larger than the particles themselves is of paramount importance, and explains why the ideal gas approximation fails at high pressures.

Heat capacity

The dimensionless heat capacity at constant volume is generally defined by

${\displaystyle {\hat{c}}_V=\frac{1}{nR}T{\left(\frac{\mathrm{\partial }S}{\mathrm{\partial }T}\right)}_V=\frac{1}{nR}{\left(\frac{\mathrm{\partial }U}{\mathrm{\partial }T}\right)}_V}$

where S is the entropy. This quantity is generally a function of temperature due to intermolecular and intramolecular forces, but for moderate temperatures it is approximately constant. Specifically, the Equipartition Theorem predicts that the constant for a monatomic gas is ĉ_V = 3/2 while for a diatomic gas it is ĉ_V = 5/2 if vibrations are neglected (which is often an excellent approximation). Since the heat capacity depends on the atomic or molecular nature of the gas, macroscopic measurements on heat capacity provide useful information on the microscopic structure of the molecules.

The dimensionless heat capacity at constant pressure of an ideal gas is:

${\displaystyle {\hat{c}}_P=\frac{1}{nR}T{\left(\frac{\mathrm{\partial }S}{\mathrm{\partial }T}\right)}_P=\frac{1}{nR}{\left(\frac{\mathrm{\partial }H}{\mathrm{\partial }T}\right)}_P={\hat{c}}_V+1}$

where H = U + PV is the enthalpy of the gas.

Sometimes, a distinction is made between an ideal gas, where ĉ_V and ĉ_P could vary with temperature, and a perfect gas, for which this is not the case.

The ratio of the constant volume and constant pressure heat capacity is the adiabatic index

${\displaystyle \gamma =\frac{c_P}{c_V}}$

For air, which is a mixture of gases, this ratio can be assumed to be 1.4 with only a small error over a wide temperature range.

Entropy

Using the results of thermodynamics only, we can go a long way in determining the expression for the entropy of an ideal gas. This is an important step since, according to the theory of thermodynamic potentials, if we can express the entropy as a function of U (U is a thermodynamic potential), volume V and the number of particles N, then we will have a complete statement of the thermodynamic behavior of the ideal gas. We will be able to derive both the ideal gas law and the expression for internal energy from it.

Since the entropy is an exact differential, using the chain rule, the change in entropy when going from a reference state 0 to some other state with entropy S may be written as ΔS where:

${\displaystyle \mathrm{\Delta }S={\int }_{S_0}^{S}dS={\int }_{T_0}^T{\left(\frac{\mathrm{\partial }S}{\mathrm{\partial }T}\right)}_{V}dT+{\int }_{V_0}^V{\left(\frac{\mathrm{\partial }S}{\mathrm{\partial }V}\right)}_{T}dV}$

where the reference variables may be functions of the number of particles N. Using the definition of the heat capacity at constant volume for the first differential and the appropriate Maxwell relation for the second we have:

${\displaystyle \mathrm{\Delta }S={\int }_{T_0}^T\frac{C_V}{T}dT+{\int }_{V_0}^V{\left(\frac{\mathrm{\partial }P}{\mathrm{\partial }T}\right)}_{V}dV.}$

Expressing C_V in terms of ĉ_V as developed in the above section, differentiating the ideal gas equation of state, and integrating yields:

${\displaystyle \mathrm{\Delta }S={\hat{c}}_{V}Nk\ln \left(\frac{T}{T_0}\right)+Nk\ln \left(\frac{V}{V_0}\right)}$

which implies that the entropy may be expressed as:

${\displaystyle S=Nk\ln \left(\frac{V{T}^{{\hat{c}}_V}}{f(N)}\right)}$

where all constants have been incorporated into the logarithm as f(N) which is some function of the particle number N having the same dimensions as VT^ĉ_V in order that the argument of the logarithm be dimensionless. We now impose the constraint that the entropy be extensive. This will mean that when the extensive parameters (V and N) are multiplied by a constant, the entropy will be multiplied by the same constant. Mathematically:

${\displaystyle S(T,aV,aN)=aS(T,V,N).}$

From this we find an equation for the function f(N)

${\displaystyle af(N)=f(aN).}$

Differentiating this with respect to a, setting a equal to 1, and then solving the differential equation yields f(N):

${\displaystyle f(N)=\mathrm{\Phi }N}$

where Φ may vary for different gases, but will be independent of the thermodynamic state of the gas. It will have the dimensions of VT^ĉ_V/N. Substituting into the equation for the entropy:

${\displaystyle \frac{S}{Nk}=\ln \left(\frac{V{T}^{{\hat{c}}_V}}{N\mathrm{\Phi }}\right).}$

and using the expression for the internal energy of an ideal gas, the entropy may be written:

${\displaystyle \frac{S}{Nk}=\ln \left[\frac{V}{N}{\left(\frac{U}{{\hat{c}}_{V}kN}\right)}^{{\hat{c}}_V}\frac{1}{\mathrm{\Phi }}\right]}$

Since this is an expression for entropy in terms of U, V, and N, it is a fundamental equation from which all other properties of the ideal gas may be derived.

This is about as far as we can go using thermodynamics alone. Note that the above equation is flawed – as the temperature approaches zero, the entropy approaches negative infinity, in contradiction to the third law of thermodynamics. In the above "ideal" development, there is a critical point, not at absolute zero, at which the argument of the logarithm becomes unity, and the entropy becomes zero. This is unphysical. The above equation is a good approximation only when the argument of the logarithm is much larger than unity – the concept of an ideal gas breaks down at low values of V/N. Nevertheless, there will be a "best" value of the constant in the sense that the predicted entropy is as close as possible to the actual entropy, given the flawed assumption of ideality. A quantum-mechanical derivation of this constant is developed in the derivation of the Sackur–Tetrode equation which expresses the entropy of a monatomic (ĉ_V = 3/2) ideal gas. In the Sackur–Tetrode theory the constant depends only upon the mass of the gas particle. The Sackur–Tetrode equation also suffers from a divergent entropy at absolute zero, but is a good approximation for the entropy of a monatomic ideal gas for high enough temperatures.

An alternative way of expressing the change in entropy:

$${\displaystyle \frac{\mathrm{\Delta }S}{Nk{\hat{c}}_V}=\ln \left(\frac{P}{P_0}\right)+\gamma \ln \left(\frac{V}{V_0}\right)=\ln \left(\frac{P{V}^{\gamma }}{P_0{V}_0^{\gamma }}\right)⟹P{V}^{\gamma }=\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{t}.\text{for isentropic process}}$$

Thermodynamic potentials

Main article: Thermodynamic potential

Expressing the entropy as a function of T, V, and N:

${\displaystyle \frac{S}{kN}=\ln \left(\frac{V{T}^{{\hat{c}}_V}}{N\mathrm{\Phi }}\right)}$

The chemical potential of the ideal gas is calculated from the corresponding equation of state (see thermodynamic potential):

${\displaystyle \mu ={\left(\frac{\mathrm{\partial }G}{\mathrm{\partial }N}\right)}_{T,P}}$

where G is the Gibbs free energy and is equal to U + PV − TS so that:

${\displaystyle \mu (T,P)=kT\left({\hat{c}}_P-\ln \left(\frac{k{T}^{{\hat{c}}_P}}{P\mathrm{\Phi }}\right)\right)}$

The chemical potential is usually referenced to the potential at some standard pressure P^o so that, with ${\displaystyle {\mu }^o(T)=\mu (T,P^o)}$:

${\displaystyle \mu (T,P)={\mu }^o(T)+kT\ln \left(\frac{P}{Po}\right)}$

For a mixture (j=1,2,...) of ideal gases, each at partial pressure P_j, it can be shown that the chemical potential μ_j will be given by the above expression with the pressure P replaced by P_j.

The thermodynamic potentials for an ideal gas can now be written as functions of T, V, and N as:

${\displaystyle U}$		${\displaystyle ={\hat{c}}_{V}NkT}$
${\displaystyle A}$	${\displaystyle =U-TS}$	${\displaystyle =\mu N-NkT}$
${\displaystyle H}$	${\displaystyle =U+PV}$	${\displaystyle ={\hat{c}}_{P}NkT}$
${\displaystyle G}$	${\displaystyle =U+PV-TS}$	${\displaystyle =\mu N}$

where, as before,

${\displaystyle {\hat{c}}_P={\hat{c}}_V+1}$.

The most informative way of writing the potentials is in terms of their natural variables, since each of these equations can be used to derive all of the other thermodynamic variables of the system. In terms of their natural variables, the thermodynamic potentials of a single-species ideal gas are:

${\displaystyle U(S,V,N)={\hat{c}}_{V}Nk{\left(\frac{N\mathrm{\Phi }}{V}{e}^{S/Nk}\right)}^{1/{\hat{c}}_V}}$

${\displaystyle A(T,V,N)=NkT\left({\hat{c}}_V-\ln \left(\frac{V{T}^{{\hat{c}}_V}}{N\mathrm{\Phi }}\right)\right)}$

${\displaystyle H(S,P,N)={\hat{c}}_{P}Nk{\left(\frac{P\mathrm{\Phi }}{k}{e}^{S/Nk}\right)}^{1/{\hat{c}}_P}}$

${\displaystyle G(T,P,N)=NkT\left({\hat{c}}_P-\ln \left(\frac{k{T}^{{\hat{c}}_P}}{P\mathrm{\Phi }}\right)\right)}$

In statistical mechanics, the relationship between the Helmholtz free energy and the partition function is fundamental, and is used to calculate the thermodynamic properties of matter; see configuration integral for more details.

Speed of sound

The speed of sound in an ideal gas is given by the Newton-Laplace formula:

${\displaystyle c_{\text{sound}}=\sqrt{\frac{K_s}{\rho }}=\sqrt{{\left(\frac{\mathrm{\partial }P}{\mathrm{\partial }\rho }\right)}_s},}$

where the isentropic Bulk modulus ${\displaystyle K_s=\rho {\left(\frac{\mathrm{\partial }P}{\mathrm{\partial }\rho }\right)}_s.}$

For an isentropic process of an ideal gas, ${\displaystyle P{V}^{\gamma }=\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{t}\Rightarrow P\propto {\left(\frac{1}{V}\right)}^{\gamma }\propto {\rho }^{\gamma }}$, therefore

${\displaystyle c_{\text{sound}}=\sqrt{{\left(\frac{\mathrm{\partial }P}{\mathrm{\partial }\rho }\right)}_s}=\sqrt{\frac{\gamma P}{\rho }}=\sqrt{\frac{\gamma RT}{M}}}$

Here,

• γ is the adiabatic index (ĉ_P/ĉ_V)
• s is the entropy per particle of the gas.
• ρ is the mass density of the gas.
• P is the pressure of the gas.
• R is the universal gas constant
• T is the temperature
• M is the molar mass of the gas.

Table of ideal gas equations

Main article: Table of thermodynamic equations § Ideal gas

Ideal quantum gases

In the above-mentioned Sackur–Tetrode equation, the best choice of the entropy constant was found to be proportional to the quantum thermal wavelength of a particle, and the point at which the argument of the logarithm becomes zero is roughly equal to the point at which the average distance between particles becomes equal to the thermal wavelength. In fact, quantum theory itself predicts the same thing. Any gas behaves as an ideal gas at high enough temperature and low enough density, but at the point where the Sackur–Tetrode equation begins to break down, the gas will begin to behave as a quantum gas, composed of either bosons or fermions. (See the gas in a box article for a derivation of the ideal quantum gases, including the ideal Boltzmann gas.)

Gases tend to behave as an ideal gas over a wider range of pressures when the temperature reaches the Boyle temperature.

Ideal Boltzmann gas

The ideal Boltzmann gas yields the same results as the classical thermodynamic gas, but makes the following identification for the undetermined constant Φ:

${\displaystyle \mathrm{\Phi }=\frac{T^{\frac{3}{2}}{\mathrm{\Lambda }}^3}{g}}$

where Λ is the thermal de Broglie wavelength of the gas and g is the degeneracy of states.

Ideal Bose and Fermi gases

An ideal gas of bosons (e.g. a photon gas) will be governed by Bose–Einstein statistics and the distribution of energy will be in the form of a Bose–Einstein distribution. An ideal gas of fermions will be governed by Fermi–Dirac statistics and the distribution of energy will be in the form of a Fermi–Dirac distribution.

Quantum technology

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Quantum_technology

Quantum technology is an emerging field of physics and engineering, encompassing technologies that rely on the properties of quantum mechanics, especially quantum entanglement, quantum superposition, and quantum tunneling. Quantum computing, sensors, cryptography, simulation, measurement, and imaging are all examples of emerging quantum technologies. The development of quantum technology also heavily impacts established fields such as space exploration.

Colloidal quantum dots irradiated with a UV light. Different sized quantum dots emit different colour light due to quantum confinement.

Secure communications

Main article: Quantum communication

Quantum secure communication is a method that is expected to be 'quantum safe' in the advent of quantum computing systems that could break current cryptography systems using methods such as Shor's algorithm. These methods include quantum key distribution (QKD), a method of transmitting information using entangled light in a way that makes any interception of the transmission obvious to the user. Another method is the quantum random number generator, which is capable of producing truly random numbers unlike non-quantum algorithms that merely imitate randomness.

Computing

Main article: Quantum computing

Quantum computers are expected to have a number of important uses in computing fields such as optimization and machine learning. They are perhaps best known for their expected ability to carry out Shor's algorithm, which can be used to factorize large numbers and is an important process in the securing of data transmissions.

Quantum simulators

Main article: Quantum simulator

Quantum simulators are types of quantum computers used to simulate a real world system and can be used to simulate chemical compounds or solve high energy physics problems. Quantum simulators are simpler to build as opposed to general purpose quantum computers because complete control over every component is not necessary. Current quantum simulators under development include ultracold atoms in optical lattices, trapped ions, arrays of superconducting qubits, and others.

Sensors

Main article: Quantum sensor

Quantum sensors are expected to have a number of applications in a wide variety of fields including positioning systems, communication technology, electric and magnetic field sensors, gravimetry as well as geophysical areas of research such as civil engineering and seismology.

History

The field of quantum technology was first outlined in a 1997 book by Gerard J. Milburn, which was then followed by a 2003 article by Jonathan P. Dowling and Gerard J. Milburn, as well as a 2003 article by David Deutsch.

Many devices already available are fundamentally reliant on the effects of quantum mechanics. These include laser systems, transistors and semiconductor devices, as well as other devices such as MRI imagers. The UK Defence Science and Technology Laboratory (DSTL) grouped these devices as 'quantum 1.0' to differentiate them from what it dubbed 'quantum 2.0', which it defined as a class of devices that actively create, manipulate, and read out quantum states of matter using the effects of superposition and entanglement.

Future Goals

In the realm of Quantum technology we are in the first couple years of its life. For each individual section of Quantum technology such as quantum computers, simulators, communications, sensors and metrology there is so much room for improvement according to Quantum in a nutshell. In the next couple years Quantum computers hope to process 50 qubits, as well as demonstrate quantum speed-up and outperforming classical computers. Quantum simulators have the capability to solve problems beyond supercomputer capacity. For more information visit Quantum technologies in a nut shell. According to quantum technology expert Paul Martin Quantum technology promises improvements in everyday gadgets such as navigation, timing systems, communication security, computers, and more accurate healthcare imaging.

Research programmes

From 2010 onwards, multiple governments have established programmes to explore quantum technologies, such as the UK National Quantum Technologies Programme, which created four quantum 'hubs', the Centre for Quantum Technologies in Singapore, and QuTech, a Dutch center to develop a topological quantum computer. In 2016, the European Union introduced the Quantum Technology Flagship, a €1 Billion, 10-year-long megaproject, similar in size to earlier European Future and Emerging Technologies Flagship projects. In December 2018, the United States passed the National Quantum Initiative Act, which provides a US$1 billion annual budget for quantum research. China is building the world's largest quantum research facility with a planned investment of 76 billion Yuan (approx. €10 Billion). Indian government has also invested 8000 crore Rupees (approx. US$1.02 Billion) over 5-years to boost quantum technologies under its National Quantum Mission.

In the private sector, large companies have made multiple investments in quantum technologies. Organizations such as Google, D-wave systems, and University of California Santa Barbara have formed partnerships and investments to develop quantum technology.

Country/Group	Name of Center/ Project	Government control (yes/no/partial)	Type of Quantum Technology Research	Established date	Funding
AUSTRALIA	Australian Research Council Centres of Excellence	Yes	Computing	2017	US$94 million
AUSTRALIA	Department of Defence’s Next Generation Technologies Fund	Yes	Integrated intelligence, surveillance and reconnaissance Space capabilities Enhanced human performance Medical countermeasure products Multi-disciplinary material sciences Quantum technologies Trusted autonomous systems Cyber Advanced sensors Hypersonics Directed energy capabilities	2016	US$4.5M
AUSTRALIA	Sydney Quantum Academy	Partial	Quantum economy	December 7, 2020	US$15.0M
AUSTRALIA	Silicon Quantum Computing	Partial	Quantum computing	May 2017	US$83M
CANADA	Canadian Space Agency Quantum Encryption and Science Satellite	Partial	Quantum key distribution(QKD)	December 2017
CANADA	National Research Council of Canada’s Security and Disruptive Technologies Research Centre: Quantum Sensors and Security program	Partial	Longer-range emerging and disruptive technologies	2012	US$23M
CANADA	Natural Sciences and Engineering Research Council/UK Research and Innovation	Partial	Quantum technology development		US$3.4M
CANADA	Canada’s National Quantum Strategy	Partial	The Strategy will guide investments along three pillars − quantum research, talent and commercialization − toward achieving three key missions, in quantum computers and software, communications and sensors.	2023	US$267M
CHINA	Chinese Academy of Sciences Center for Excellence in Quantum Information and Quantum Physics	Yes	General	May 2015	US$10.0B
CHINA	Quantum Experiments at Space Scale (QUESS) project (the Micius satellite)	Yes	Quantum key distribution	May 2015
CHINA	Beijing–Shanghai Quantum Secure Communication Backbone	Yes	Quantum Communications	May 2015
CHINA	National Quantum Laboratory	Yes	Quantum metrology and building a quantum computer	May 2015 (opened in 2020)
EUROPEAN UNION	Quantum Technologies Flagship program	Yes	Quantum computing Quantum simulation Quantum communication Quantum metrology and sensing	2018	Expected budget of €1 billion
EUROPEAN UNION	Coordination and support action for Quantum Technology Education (QTEdu)	Yes	Education	2020
EUROPEAN UNION	QuantERA	Yes	Quantum technologies	2016	€89 million
EUROPEAN UNION	Open European Quantum Key Distribution (OpenQKD)	Yes	Quantum-based cryptography	Sept. 2, 2019 (ended Sept. 1, 2022)	€17 974 246,25
EUROPEAN UNION	European Quantum Communication Infrastructure (EuroQCI)	Yes	Quantum communication infrastructure	June 2019	€90,000,000
FRANCE	National Strategy for Quantum Technologies	Yes	Quantum computing, quantum communications and quantum sensors	January 21, 2021	US$1.8B
GERMANY	Quantum Technologies — From Basic Research to Market	Yes	Quantum technologies	September 26, 2018	€650M
GERMANY	Agenda Quantensysteme 2030	Yes	quantum computing, quantum simulation, quantum communication, quantum sensors, supporting technologies, public outreach	March 23, 2021.
GERMANY	Fraunhofer-Gesellschaft-IBM collaboration	Yes	Quantum computing	September, 2019	€40M
GERMANY	QuNET	Yes	Quantum communication	2018	€165M
INDIA	National Mission on Quantum Technologies & Applications	Yes	Quantum communication, quantum simulation, quantum computation, Quantum sensing, and quantum metrology	2020	Rs 8000 Crore
ISRAEL	National Program for Quantum Science and Technology	Yes	National quantum development	2019	US$360
JAPAN.	Quantum Technology Innovation Strategy	Yes	Quantum technology	2020	US$470
JAPAN	Quantum Strategic Industry Alliance for Revolution (Q-STAR)	Yes	An industry council to promote quantum technologies	September 1, 2021
JAPAN	Quantum Leap Flagship Program	Yes	Superconducting quantum computer, quantum simulation, quantum computing, solid state quantum sensors, lasers	2018	US$200M
JAPAN	The Moonshot Research and Development Program (Goal 6)	Yes	Quantum computing	2019	US$963M for total program not just quantum
NETHERLANDS	National Agenda for Quantum Technology: Quantum Delta NL	Yes	Quantum computing,quantum communication, and quantum sensing	2020	€615M
RUSSIA	Rosatom	Yes	Quantum technologies and research infrastructure	2021	23 billion rubles
RUSSIA	RZD (Russian Railways)	Yes	Quantum Communications	October 2021	138M Russian rubles
SINGAPORE	Quantum Engineering Program	Yes	Quantum technology	2018	US$121.6M
SINGAPORE	Centre for Quantum Technologies (CQT)	Yes	Quantum Technologies	2007	US$194.9M
SINGAPORE	SGInnovate- Quantum Technologies	Yes	Digital financing	2015
SOUTH KOREA	Quantum Computing Technology Development Project	Yes	Quantum technologies	2019	US$39.8M
UNITED KINGDOM	National Quantum Technologies Programme	Yes	Funding UK quantum technologies	2013	US$1B
UNITED KINGDOM	National Quantum Computing Centre	Yes	Quantum computing	Set to open in 2023	£93m
UNITED KINGDOM	Rigetti Computing	Partial	Quantum computing	2013	US$268m
UNITED STATES	Quantum Industry Consortium	Yes	General "quantum ecosystem" (quantum industry supply chain, federal R&D investment priorities, standards and regulation, industry interactions, etc.)	2018	US$1.25B
UNITED STATES	National Quantum Coordination Office	Yes	Quantum technology research and development	2019
UNITED STATES	The Department of Energy Office of Science	Yes	Quantum computing, quantum algorithms, quantum sensors, quantum processors, quantum networks and quantum simulation	2019	US$900M (US$300M in FY 2023)
UNITED STATES	The National Science Foundation (Five Quantum Leap Challenges Institutes)	Yes	Quantum computing, quantum sensors, quantum processors, quantum biological sensing, and quantum simulation	2020	US$125M
UNITED STATES	National Quantum Initiative Act	Yes	Quantum information science and Quantum technology development	Dec. 21, 2018	US$1.275B
UNITED STATES	MonArk Quantum Foundry	Partial	Development of quantum materials and devices	August 17, 2021	US$19,990,000
UNITED STATES	Center for Quantum Networks	Partial	Quantum computing	2020	US$26 m
UNITED STATES	National Q-12 Education Partnership	Yes	Education	2020	US$1M

Biodegradable plastic

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Biodegradable_plastic

Disposable plastic cups made from biodegradable plastic

Biodegradable plastics are plastics that can be decomposed by the action of living organisms, usually microbes, into water, carbon dioxide, and biomass. Biodegradable plastics are commonly produced with renewable raw materials, micro-organisms, petrochemicals, or combinations of all three.

While the words "bioplastic" and "biodegradable plastic" are similar, they are not synonymous. Not all bioplastics (plastics derived partly or entirely from biomass) are biodegradable, and some biodegradable plastics are fully petroleum based. As more companies are keen to be seen as having "Green" credentials, solutions such as using bioplastics are being investigated and implemented more. The definition of bioplastics is still up for debate. The phrase is frequently used to refer to a wide range of diverse goods that may be biobased, biodegradable, or both. This could imply that polymers made from oil can be branded as "bioplastics" even if they have no biological components at all. However there are many skeptics who believe that bioplastics will not solve problems others expect.

History

Polyhydroxyalkanoate (PHA) was first observed in bacteria in 1888 by Martinus Beijerinck. In 1926, French microbiologist Maurice Lemoigne chemically identified the polymer after extracting it from Bacillus megaterium. It was not until the early 1960s that the groundwork for scaled production was laid. Several patents for the production and isolation of PHB, the simplest PHA, were administered to W.R. Grace & Co. (USA), but as a result of low yields, tainted product and high extraction costs, the operation was dissolved. When OPEC halted oil exports to the US to boost global oil prices in 1973, more plastic and chemical companies began making significant investment in the biosynthesis of sustainable plastics. As a result, Imperial Chemical Industries (ICI UK) successfully produced PHB at a yield of 70% using the strain Alcaligenes latus. The specific PHA produced in this instance was a scl-PHA. Production efforts slowed dramatically due to the undesirable properties of the PHA produced and the diminishing threat of rising oil prices soon thereafter.

In 1983, ICI received venture capital funding and founded Marlborough Biopolymers to manufacture the first broad-application biodegradable plastic, PHBV, named Biopol. Biopol is a copolymer composed of PHB and PHV, but was still too costly to produce to disrupt the market. In 1996, Monsanto discovered a method of producing one of the two polymers in plants and acquired Biopol from Zeneca, a spinout of ICI, as a result of the potential for cheaper production.

As a result of the steep increase in oil prices in the early 2000s (to nearly $140/barrel US$ in 2008), the plastic-production industry finally sought to implement these alternatives to petroleum-based plastics. Since then, countless alternatives, produced chemically or by other bacteria, plants, seaweed and plant waste have sprung up as solutions. Geopolitical factors also impact their use.

Application

Biodegradable plastics are commonly used for disposable items, such as packaging, cutlery, and food service containers.

In principle, biodegradable plastics could replace many applications for conventional plastics. However, this entails a number of challenges.

• Many biodegradable plastics are designed to degrade in industrial composting systems. However, this requires a well-managed waste system to ensure that this actually happens. If products made from these plastics are discarded into conventional waste streams such as landfill, or find their way into the open environment such as rivers and oceans, potential environmental benefits are not realised and evidence indicates that this can actually worsen, rather than reduce, the problem of plastic pollution.
• Plastic items labelled as 'biodegradable', but that only break down into smaller pieces like microplastics, or into smaller units that are not biodegradable, are not an improvement over conventional plastic.
• A 2009 study found that the use of biodegradable plastics was financially viable only in the context of specific regulations which limit the usage of conventional plastics. For example, biodegradable plastic bags have been compulsory in Italy since 2011 with the introduction of a specific law.

Types

Development of biodegradable containers

Bio-based plastics

Development of an edible casein film overwrap at USDA

Biologically synthesized plastics (also called bioplastics or biobased plastics) are plastics produced from natural origins, such as plants, animals, or micro-organisms.

Polyhydroxyalkanoates (PHAs)

Polyhydroxyalkanoates are a class of biodegradable plastic naturally produced by various micro-organisms (example: Cuprividus necator). Specific types of PHAs include poly-3-hydroxybutyrate (PHB), polyhydroxyvalerate (PHV) and polyhydroxyhexanoate (PHH). The biosynthesis of PHA is usually driven by depriving organisms of certain nutrients (e.g. lack of macro elements such as phosphorus, nitrogen, or oxygen) and supplying an excess of carbon sources. PHA granules are then recovered by rupturing the micro-organisms.

PHA can be further classified into two types:

• scl-PHA from hydroxy fatty acids with short chain lengths including three to five carbon atoms are synthesized by numerous bacteria, including Cupriavidus necator and Alcaligenes latus (PHB).
• mcl-PHA from hydroxy fatty acids with medium chain lengths including six to 14 carbon atoms, can be made for example, by Pseudomonas putida.

Polylactic acid (PLA)

Polylactic acid is thermoplastic aliphatic polyester synthesized from renewable biomass, typically from fermented plant starch such as from corn, cassava, sugarcane or sugar beet pulp. In 2010, PLA had the second-highest consumption volume of any bioplastic of the world.

PLA is compostable, but non-biodegradable according to American and European standards because it does not biodegrade outside of artificial composting conditions (see § Compostable plastics).

Starch blends

Starch blends are thermoplastic polymers produced by blending starch with plasticizers. Because starch polymers on their own are brittle at room temperature, plasticizers are added in a process called starch gelatinization to augment its crystallization. While all starches are biodegradable, not all plasticizers are. Thus, the biodegradability of the plasticizer determines the biodegradability of the starch blend.

Biodegradable starch blends include starch/polylactic acid, starch/polycaprolactone, and starch/polybutylene-adipate-co-terephthalate.

Others blends such as starch/polyolefin are not biodegradable.

Cellulose-based plastics

Cellulose bioplastics are mainly the cellulose esters, (including cellulose acetate and nitrocellulose) and their derivatives, including celluloid. Cellulose can become thermoplastic when extensively modified. An example of this is cellulose acetate, which is expensive and therefore rarely used for packaging.

Lignin-based polymer composites

Lignin-based polymer composites are bio-renewable natural aromatic polymers with biodegradable properties. Lignin is found as a byproduct of polysaccharide extraction from plant material through the production of paper, ethanol, and more. It is high in abundance with reports showing that 50 million tons are being created by chemical pulp industries each year. Lignin is useful due to its low weight material and the fact that it is more environmentally friendly than other alternatives. Lignin is neutral to CO₂ release during the biodegradation process. Other biodegradable plastic processes such as polyethylene terephthalate (PET) have been found to release CO₂ and water as waste products produced by the degrading microorganisms.

Lignin contains comparable chemical properties in comparison to current plastic chemicals, which includes reactive functional groups, the ability to form into films, high carbon percentage, and it shows versatility in relation to various chemical mixtures used with plastics. Lignin is also stable, and contains aromatic rings. It is both elastic and viscous yet flows smoothly in the liquid phase. Most importantly lignin can improve on the current standards of plastics because it is antimicrobial in nature. It is being produced at such great quantities and is readily available for use as an emerging environmentally friendly polymer.

Petroleum-based plastics

Petroleum-based plastics are derived from petrochemicals, which are obtained from fossil crude oil, coal or natural gas. The most widely used petroleum-based plastics such as polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), and polystyrene (PS) are not biodegradable. However, the following petroleum-based plastics listed are.

Polyglycolic acid (PGA)

Polyglycolic acid is a thermoplastic polymer and an aliphatic polyester. PGA is often used in medical applications such as PGA sutures for its biodegradability. The ester linkage in the backbone of polyglycolic acid gives it hydrolytic instability. Thus polyglycolic acid can degrade into its nontoxic monomer, glycolic acid, through hydrolysis. This process can be expedited with esterases. In the body, glycolic acid can enter the tricarboxylic acid cycle, after which can be excreted as water and carbon dioxide.

Polybutylene succinate (PBS)

Polybutylene succinate is a thermoplastic polymer resin that has properties comparable to propylene. It is used in packaging films for food and cosmetics. In the agricultural field, PBS is used as a biodegradable mulching film PBS can be degraded by Amycolatopsis sp. HT-6 and Penicillium sp. strain 14-3. In addition, Microbispora rosea, Excellospora japonica and E. viridilutea have been shown to consume samples of emulsified PBS.

Polycaprolactone (PCL)

Polycaprolactone has gained prominence as an implantable biomaterial because the hydrolysis of its ester linkages offers its biodegradable properties. It has been shown that Bacillota and Pseudomonadota can degrade PCL. Penicillium sp. strain 26-1 can degrade high density PCL; though not as quickly as thermotolerant Aspergillus sp. strain ST-01. Species of clostridium can degrade PCL under anaerobic conditions.

Poly(vinyl alcohol) (PVA, PVOH)

Poly(vinyl alcohol) is one of the few biodegradable vinyl polymers that is soluble in water. Due to its solubility in water (an inexpensive and harmless solvent), PVA has a wide range of applications including food packaging, textiles coating, paper coating, and healthcare products.

Polybutylene adipate terephthalate (PBAT)

Polybutylene adipate terephthalate (PBAT) is a biodegradable random copolymer.

Home compostable plastics

No international standard has been established to define home-compostable plastics (i.e. those which do not rely on industrial composting facilities), but national standards have been created in Australia (AS 5810 "biodegradable plastics suitable for home composting") and in France (NF T 51-800 "Specifications for plastics suitable for home composting"). The French standard is based on the "OK compost home certification scheme", developed by Belgian certifier TÜV Austria Belgium. The following are examples of plastics that have conformed to an established national standard for home compostability:

• BioPBS FD92 resin, maximum thickness 85 microns
• BWC BF 90A resin, maximum thickness 81 microns
• Ecopond Flex 162 resin, maximum thickness 65 microns
• HCPT-1 triple laminate, maximum thickness 119 microns
• HCFD-2 duplex laminate, maximum thickness 69 microns
• Torise TRBF90 resin, maximum thickness 43 microns

Factors affecting biodegradation

One of the challenges for the design and use of biodegradable plastics is that biodegradability is a "system property". That is, whether a particular plastic item will biodegrade depends not only on the intrinsic properties of the item, but also on the conditions in the environment in which it ends up. The rate at which plastic biodegrades in a specific ecosystem depends on a wide range of environmental conditions, including temperature and the presence of specific microorganisms.

Intrinsic factors

Chemical composition:

• Least to greatest resistance to biodegradation: n-alkanes > branched alkanes > low molecular weight aromatics > cyclic alkanes > high molecular weight aromatics = polar polymers

Physical properties:

• Shape
• Exposed surface area
• Thickness

Extrinsic factors

Abiotic factors:

• Temperature
• Atmospheric water/salt concentration
• Photo-degradation
• Hydrolysis

Biotic factors:

• Presence of proper strains of microorganisms

Controversy

Though the terms "compostable, "bioplastics", and "oxo-degradative plastics" are often used in place of "biodegradable plastics", these terms are not synonymous. The waste management infrastructure currently recycles regular plastic waste, incinerates it, or places it in a landfill. Mixing biodegradable plastics into the regular waste infrastructure poses some dangers to the environment. Thus, it is crucial to identify how to correctly decompose alternative plastic materials.

Compostable plastics

Both compostable plastics and biodegradable plastics are materials that break down into their organic constituents; however, composting of some compostable plastics requires strict control of environmental factors, including higher temperatures, pressure and nutrient concentration, as well as specific chemical ratios. These conditions can only be recreated in industrial composting plants, which are few and far between. Thus, some plastics that are compostable can degrade only under highly controlled environments. Additionally, composting typically takes place in aerobic environments, while biodegradation may take place in anaerobic environments. Biologically-based polymers, sourced from non-fossil materials, can decompose naturally in the environment, whereas some plastics products made from biodegradable polymers require the assistance of anaerobic digesters or composting units to break down synthetic material during organic recycling processes.

Contrary to popular belief, non-biodegradable compostable plastics do indeed exist. These plastics will undergo biodegradation under composting conditions but will not begin degrading until they are met. In other words, these plastics cannot be claimed as “biodegradable” (as defined by both American and European Standards) due to the fact that they cannot biodegrade naturally in the biosphere. An example of a non-biodegradable compostable plastic is polylactic acid (PLA).

The ASTM standard definition outlines that a compostable plastic has to become "not visually distinguishable" at the same rate as something that has already been established as being compostable under the traditional definition.

Bioplastics

A plastic is considered a bioplastic if it was produced partly or wholly with biologically sourced polymers. A plastic is considered biodegradable if it can degrade into water, carbon dioxide, and biomass in a given time frame (dependent on different standards). Thus, the terms are not synonymous. Not all bioplastics are biodegradable. An example of a non-biodegradable bioplastic is bio-based PET. PET is a petrochemical plastic, derived from fossil fuels. Bio-based PET is the same plastic but synthesized with bacteria. Bio-based PET has identical technical properties to its fossil-based counterpart.

Oxo-degradable plastics

In addition, oxo-degradable plastics are commonly perceived to be biodegradable. However, they are simply conventional plastics with additives called prodegredants that accelerate the oxidation process. While oxo-degradable plastics rapidly break down through exposure to sunlight and oxygen, they persist as huge quantities of microplastics rather than any biological material.

Oxo-degradable plastics cannot be classified as biodegradable under American and European standards because they take too long to break down and leave plastic fragments not capable of being consumed by microorganisms. Although intended to facilitate biodegradation, oxo-degradable plastics often do not fragment optimally for microbial digestion.

Consumer labelling and greenwashing

Main article: Greenwashing

All materials are inherently biodegradable, whether it takes a few weeks or a million years to break down into organic matter and mineralize. Therefore, products that are classified as “biodegradable” but whose time and environmental constraints are not explicitly stated are misinforming consumers and lack transparency. Normally, credible companies convey the specific biodegradable conditions of their products, highlighting that their products are in fact biodegradable under national or international standards. Additionally, companies that label plastics with oxo-biodegradable additives as entirely biodegradable contribute to misinformation. Similarly, some brands may claim that their plastics are biodegradable when, in fact, they are non-biodegradable bioplastics.

In 2021, the European Commission's Scientific Advice Mechanism conducted an evidence review on biodegradable plastics and concluded that:

Labelling plastic items as ‘biodegradable’, without explaining what conditions are needed for them to biodegrade, causes confusion among consumers and other users. It could lead to contamination of waste streams and increased pollution or littering. Clear and accurate labelling is needed so that consumers can be confident of what to expect from plastic items, and how to properly use and dispose of them.

In response, the European Commission's Group of Chief Scientific Advisors recommended in 2021 to develop "coherent testing and certification standards for biodegradation of plastic in the open environment", including "testing and certification schemes evaluating actual biodegradation of biodegradable plastics in the context of their application in a specific receiving open environment".

Environmental impacts

Environmental benefits

Microbial degradation: The primary purpose of biodegradable plastics is to replace traditional plastics that persist in landfills and harm the environment. Therefore, the ability of microorganisms to break down these plastics is an incredible environmental advantage. Microbial degradation is accomplished by 3 steps: colonization of the plastic surface, hydrolysis, and mineralization. First, microorganisms populate the exposed plastics. Next, the bacteria secrete enzymes that bind to the carbon source or polymer substrates and then split the hydrocarbon bonds. The process results in the production of H₂O and CO₂. Despite the release of CO₂ into the environment, biodegradable plastics leave a smaller footprint than petroleum-based plastics that accumulate in landfills and cause heavy pollution, which is why they are explored as alternatives to traditional plastics.

Municipal solid waste: According to a 2010 report of the United States Environmental Protection Agency (EPA) the US had 31 million tons of plastic waste, representing 12.4% of all municipal solid waste. Of that, 2.55 million tons were recovered. This 8.2% recovery was much less than the 34.1% overall recovery percentage for municipal solid waste.

Depressed plastics recovery rates can be attributed to conventional plastics are often commingled with organic wastes (food scraps, wet paper, and liquids), leading to accumulation of waste in landfills and natural habitats. On the other hand, composting of these mixed organics (food scraps, yard trimmings, and wet, non-recyclable paper) is a potential strategy for recovering large quantities of waste and dramatically increasing community recycling goals. As of 2015, food scraps and wet, non-recyclable paper respectively comprise 39.6 million and 67.9 million tons of municipal solid waste.

Biodegradable plastics can replace the non-degradable plastics in these waste streams, making municipal composting a significant tool to divert large amounts of otherwise nonrecoverable waste from landfills. Compostable plastics combine the utility of plastics (lightweight, resistance, relative low cost) with the ability to completely and fully compost in an industrial compost facility. Rather than worrying about recycling a relatively small quantity of commingled plastics, proponents argue that certified biodegradable plastics can be readily commingled with other organic wastes, thereby enabling composting of a much larger portion of nonrecoverable solid waste.

Commercial composting for all mixed organics then becomes commercially viable and economically sustainable. More municipalities can divert significant quantities of waste from overburdened landfills since the entire waste stream is now biodegradable and therefore easier to process. This move away from the use of landfills may help alleviate the issue of plastic pollution.

The use of biodegradable plastics, therefore, is seen as enabling the complete recovery of large quantities of municipal solid waste (via aerobic composting and feedstocks) that have heretofore been unrecoverable by other means except land filling or incineration.

Environmental concerns

Oxo-biodegradation

There are allegations that biodegradable plastic bags may release metals, and may require a great deal of time to degrade in certain circumstances and that OBD (oxo-biodegradable) plastics may produce tiny fragments of plastic that do not continue to degrade at any appreciable rate regardless of the environment. The response of the Oxo-biodegradable Plastics Association (www.biodeg.org) is that OBD plastics do not contain metals. They contain salts of metals, which are not prohibited by legislation and are in fact necessary as trace-elements in the human diet. Oxo-biodegradation of low-density polyethylene containing a proprietary manganese-salt-based additive showed 91% biodegradation in a soil environment after 24 months.

Effect on food supply

There is also much debate about the total carbon, fossil fuel and water usage in manufacturing biodegradable bioplastics from natural materials and whether they are a negative impact to human food supply. To make 1 kg (2.2 lb) of polylactic acid, the most common commercially available compostable plastic, 2.65 kg (5.8 lb) of corn is required. Since as of 2010, approximately 270 million tonnes of plastic are made every year, replacing conventional plastic with corn-derived polylactic acid would remove 715.5 million tonnes from the world's food supply, at a time when global warming is reducing tropical farm productivity.

Methane release

There is concern that another greenhouse gas, methane, might be released when any biodegradable material, including truly biodegradable plastics, degrades in an anaerobic landfill environment. Methane production from 594 managed landfill environments is captured and used for energy; some landfills burn this off through a process called flaring to reduce the release of methane into the environment. In the US, most landfilled materials today go into landfills where they capture the methane biogas for use in clean, inexpensive energy. Incinerating non-biodegradable plastics will release carbon dioxide as well. Disposing of non-biodegradable plastics made from natural materials in anaerobic (landfill) environments will result in the plastic lasting for hundreds of years.

Biodegradation in the ocean

Biodegradable plastics that have not fully degraded are disposed of in the oceans by waste management facilities with the assumption that the plastics will eventually break down in a short amount of time. However, the ocean is not optimal for biodegradation, as the process favors warm environments with an abundance of microorganisms and oxygen. Remaining microfibers that have not undergone biodegradation can cause harm to marine life.

Energy costs for production

Various researchers have undertaken extensive life cycle assessments of biodegradable polymers to determine whether these materials are more energy efficient than polymers made by conventional fossil fuel-based means. Research done by Gerngross, et al. estimates that the fossil fuel energy required to produce a kilogram of polyhydroxyalkanoate (PHA) is 50.4 MJ/kg, which coincides with another estimate by Akiyama, et al., who estimate a value between 50-59 MJ/kg. This information does not take into account the feedstock energy, which can be obtained from non-fossil fuel based methods. Polylactide (PLA) was estimated to have a fossil fuel energy cost of 54-56.7 from two sources, but recent developments in the commercial production of PLA by NatureWorks has eliminated some dependence of fossil fuel-based energy by supplanting it with wind power and biomass-driven strategies. They report making a kilogram of PLA with only 27.2 MJ of fossil fuel-based energy and anticipate that this number will drop to 16.6 MJ/kg in their next generation plants. In contrast, polypropylene and high-density polyethylene require 85.9 and 73.7 MJ/kg, respectively,^[67] but these values include the embedded energy of the feedstock because it is based on fossil fuel.

Gerngross reports a 2.65 kg total fossil fuel energy equivalent (FFE) required to produce a single kilogram of PHA, while polyethylene only requires 2.2 kg FFE. Gerngross assesses that the decision to proceed forward with any biodegradable polymer alternative will need to take into account the priorities of society with regard to energy, environment, and economic cost.

Furthermore, it is important to realize the youth of alternative technologies. Technology to produce PHA, for instance, is still in development today, and energy consumption can be further reduced by eliminating the fermentation step, or by utilizing food waste as feedstock. The use of alternative crops other than corn, such as sugar cane from Brazil, are expected to lower energy requirements. For instance, "manufacturing of PHAs by fermentation in Brazil enjoys a favorable energy consumption scheme where bagasse is used as source of renewable energy."

Many biodegradable polymers that come from renewable resources (i.e. starch-based, PHA, PLA) also compete with food production, as the primary feedstock is currently corn. For the US to meet its current output of plastics production with BPs, it would require 1.62 square meters per kilogram produced.

Regulations/standards

To ensure the integrity of products labelled as "biodegradable", the following standards have been established:

United States

The Biodegradable Products Institute (BPI) is the primary certification organization in the US. ASTM International defines methods to test for biodegradable plastic, both anaerobically and aerobically, as well as in marine environments. The specific subcommittee responsibility for overseeing these standards falls on the Committee D20.96 on Environmentally Degradable Plastics and Bio based Products. The current ASTM standards are defined as standard specifications and standard test methods. Standard specifications create a pass or fail scenario whereas standard test methods identify the specific testing parameters for facilitating specific time frames and toxicity of biodegradable tests on plastics.

Anaerobic conditions

Test methodology	Title
ASTM D5511-18	Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under High-Solids Anaerobic-Digestion Conditions
ASTM D5526-18	Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under Accelerated Landfill Conditions

Both standards above indicate that a minimum of 70% of the material should have biodegraded by 30 days (ASTM D5511-18) or the duration of the testing procedure (ASTM D5526-18) to be considered biodegradable under anaerobic conditions. Test methodologies provide guidelines on testing but provide no pass/fail guidance on results.

Aerobic conditions

Specification	Title
ASTM D6400	Standard Specification for Labeling of Plastics Designed to be Aerobically Composted in Municipal or Industrial Facilities
ASTM D6868	Standard Specification for Labeling of End Items that Incorporate Plastics and Polymers as Coatings or Additives with Paper and Other Substrates Designed to be Aerobically Composted in Municipal or Industrial Facilities

Both standards above outline procedures for testing and labelling biodegradability in aerobic composting conditions. Plastics can be classified as biodegradable in aerobic environments when 90% of the material is fully mineralized into CO₂ within 180 days (~6 months). Specifications carry pass/fail criteria and reporting.

European Union standards

Anaerobic conditions

Standard	Title
EN 13432:2000	Packaging: requirements for packaging recoverable through composting and biodegradation

Similar to the US standards, the European standard requires that 90% of the polymer fragments be fully mineralized into CO₂ within 6 months.

Aerobic conditions

Standard	Title
EN 14046:2004	Evaluation of the ultimate aerobic biodegradability and disintegration of packaging materials under controlled composting conditions.

Future European standards

In 2021, the European Commission's Scientific Advice Mechanism recommended to the Commission to develop new certification and testing standards for biodegradation of plastic in the open environment, including:

• evaluation of actual biodegradation performance, and assessment of environmental risks, in specific open environments such as soils, rivers and oceans
• testing of biodegradation under laboratory and simulated environmental conditions
• development of a materials catalogue and relative biodegradation rates in a range of environments
• "clear and effective labelling" for consumers, manufacturers and vendors to ensure proper disposal of biodegradable plastics.

In November 2022, the European Commission proposed an EU regulation to replace the 1994 Packaging and packaging waste directive, along with a communication to clarify the labels biobased, biodegradable, and compostable.

British standards

In October 2020 British Standards published new standards for biodegradable plastic. In order to comply with the standards biodegradable plastic must degrade to a wax which contains no microplastics or nanoplastics within two years. The breakdown of the plastics can be triggered by exposure to sunlight, air and water. Chief executive of Polymateria, Niall Dunne, said his company had created polyethylene film which degraded within 226 days and plastic cups which broke down in 336 days.

Role of genetic engineering and synthetic biology

With rising concern for environmental ramifications of plastic waste, researchers have been exploring the application of genetic engineering and synthetic biology for optimizing biodegradable plastic production. This involves altering the endogenous genetic makeup or other biological systems of organisms.

In 1995, an article titled “Production of Polyhydroxyalkanoates, a Family of Biodegradable Plastics and Elastomers, in Bacteria and Plants” describes the use of synthetic biology to increase the yield of polyhydroxyalkanoates (PHAs), specifically in Arabidopsis plants. Similarly, a study conducted in 1999 investigated how the oil seed rape plant can be genetically modified to produce PHBVs. Although a high yield was not produced, this displays the early use of genetic engineering for production of biodegradable plastics.

Efforts are still being made in the direction of biodegradable plastic production through genetic fabrication and re-design. A paper published in 2014 titled “Genetic engineering increases yield of biodegradable plastic from cyanobacteria” outlines procedures conducted to produce a higher yield of PHBs that is industrially comparable. Previous research indicated that both Rre37 and SigE proteins are separately responsible for the activation of PHB production in the Synechocystis strain of cyanobacteria. Thus, in this study, the Synechocystis strain was modified to overexpress Rre37 and SigE proteins together under nitrogen-limited conditions.

Currently, a student-run research group at the University of Virginia (Virginia iGEM 2019) is in the process of genetically engineering Escherichia coli to convert styrene (monomer of polystyrene) into P3HBs (a type of PHA). The project aims to demonstrate that waste polystyrene can effectively be used as a carbon source for biodegradable plastic production, tackling both issues of polystyrene waste accumulation in landfills and high production cost of PHAs.

Biodegradable conducting polymers in the medical field

Biodegradable Conducting Polymers (CPs) are a polymeric material designed for applications within the human body. Important properties of this material are its electrical conductivity comparable to traditional conductors and its biodegradability. The medical applications of biodegradable CPs are attractive to medical specialties such as tissue engineering and regenerative medicine. In tissue engineering, the key focus is on providing damaged organs with physicochemical cues to damaged organs for repair. This is achieved through use of nanocomposite scaffolding. Regenerative medicine applications are designed to regenerate cells along with improving the repair process of the body. The use of biodegradable CPs can also be implemented into biomedical imaging along with implants, and more.

The design of biodegradable CPs began with the blending of biodegradable polymers including polylactides, polycaprolactone, and polyurethanes. This design triggered innovation into what is being engineered as of the year 2019. The current biodegradable CPs is applicable for use in the biomedical field. The compositional architecture of current biodegradable CPs includes the conductivity properties of oligomer-based biodegradable polymers implemented into compositions of linear, starshaped, or hyperbranched formations. Another implementation to enhance the biodegradable architecture of the CPs is by use of monomers and conjugated links that are degradable. The biodegradable polymers used in biomedical applications typically consist of hydrolyzable esters and hydrazones. These molecules, upon external stimulation, go on to be cleaved and broken down. The cleaving activation process can be achieved through use of an acidic environment, increasing the temperature, or by use of enzymes. Three categories of biodegradable CP composites have been established in relation to their chemistry makeup. The first category includes partially biodegradable CP blends of conductive and biodegradable polymeric materials. The second category includes conducting oligomers of biodegradable CPs. The third category is that of modified and degradable monpmer units along with use of degradable conjugated links for use in biodegradable CPs polymers.