Wave power

From Wikipedia, the free encyclopedia

Pelamis Wave Energy Converter on site at the European Marine Energy Centre (EMEC), in 2008

 

Azura at the US Navy’s Wave Energy Test Site (WETS) on Oahu

 

The mWave converter by Bombora Wave Power

 

Wave Power Station using a pneumatic Chamber

 

Wave power is the capture of energy of wind waves to do useful work – for example, electricity generation, water desalination, or pumping water. A machine that exploits wave power is a wave energy converter (WEC). 

Wave power is distinct from tidal power, which captures the energy of the current caused by the gravitational pull of the Sun and Moon. Waves and tides are also distinct from ocean currents which are caused by other forces including breaking waves, wind, the Coriolis effect, cabbeling, and differences in temperature and salinity.

Wave-power generation is not a widely employed commercial technology, although there have been attempts to use it since at least 1890.

In 2000 the world's first commercial Wave Power Device, the Islay LIMPET was installed on the coast of Islay in Scotland and connected to the National Grid. In 2008, the first experimental multi-generator wave farm was opened in Portugal at the Aguçadoura Wave Park.

Physical concepts

When an object bobs up and down on a ripple in a pond, it follows approximately an elliptical trajectory.

 

Motion of a particle in an ocean wave. A = At deep water. The elliptical motion of fluid particles decreases rapidly with increasing depth below the surface. B = At shallow water (ocean floor is now at B). The elliptical movement of a fluid particle flattens with decreasing depth. 1 = Propagation direction. 2 = Wave crest. 3 = Wave trough.

 

Photograph of the elliptical trajectories of water particles under a – progressive and periodic – surface gravity wave in a wave flume. The wave conditions are: mean water depth d = 2.50 ft (0.76 m), wave height H = 0.339 ft (0.103 m), wavelength λ = 6.42 ft (1.96 m), period T = 1.12 s.

 

Waves are generated by wind passing over the surface of the sea. As long as the waves propagate slower than the wind speed just above the waves, there is an energy transfer from the wind to the waves. Both air pressure differences between the upwind and the lee side of a wave crest, as well as friction on the water surface by the wind, making the water to go into the shear stress causes the growth of the waves.

Wave height is determined by wind speed, the duration of time the wind has been blowing, fetch (the distance over which the wind excites the waves) and by the depth and topography of the seafloor (which can focus or disperse the energy of the waves). A given wind speed has a matching practical limit over which time or distance will not produce larger waves. When this limit has been reached the sea is said to be "fully developed". 

In general, larger waves are more powerful but wave power is also determined by wave speed, wavelength, and water density. 

Oscillatory motion is highest at the surface and diminishes exponentially with depth. However, for standing waves (clapotis) near a reflecting coast, wave energy is also present as pressure oscillations at great depth, producing microseisms. These pressure fluctuations at greater depth are too small to be interesting from the point of view of wave power. 

The waves propagate on the ocean surface, and the wave energy is also transported horizontally with the group velocity. The mean transport rate of the wave energy through a vertical plane of unit width, parallel to a wave crest, is called the wave energy flux (or wave power, which must not be confused with the actual power generated by a wave power device).

Wave power formula

In deep water where the water depth is larger than half the wavelength, the wave energy flux is

${\displaystyle P={\frac {\rho g^{2}}{64\pi }}H_{m0}^{2}T_{e}\approx \left(0.5{\frac {\text{kW}}{{\text{m}}^{3}\cdot {\text{s}}}}\right)H_{m0}^{2}\;T_{e},}$

with P the wave energy flux per unit of wave-crest length, H_m0 the significant wave height, T_e the wave energy period, ρ the water density and g the acceleration by gravity. The above formula states that wave power is proportional to the wave energy period and to the square of the wave height. When the significant wave height is given in metres, and the wave period in seconds, the result is the wave power in kilowatts (kW) per metre of wavefront length.

Example: Consider moderate ocean swells, in deep water, a few km off a coastline, with a wave height of 3 m and a wave energy period of 8 seconds. Using the formula to solve for power, we get

${\displaystyle P\approx 0.5{\frac {\text{kW}}{{\text{m}}^{3}\cdot {\text{s}}}}(3\cdot {\text{m}})^{2}(8\cdot {\text{s}})\approx 36{\frac {\text{kW}}{\text{m}}},}$

meaning there are 36 kilowatts of power potential per meter of wave crest. 

In major storms, the largest waves offshore are about 15 meters high and have a period of about 15 seconds. According to the above formula, such waves carry about 1.7 MW of power across each metre of wavefront. 

An effective wave power device captures as much as possible of the wave energy flux. As a result, the waves will be of lower height in the region behind the wave power device.

Wave energy and wave-energy flux

In a sea state, the average(mean) energy density per unit area of gravity waves on the water surface is proportional to the wave height squared, according to linear wave theory:

${\displaystyle E={\frac {1}{16}}\rho gH_{m0}^{2},}$

where E is the mean wave energy density per unit horizontal area (J/m²), the sum of kinetic and potential energy density per unit horizontal area. The potential energy density is equal to the kinetic energy, both contributing half to the wave energy density E, as can be expected from the equipartition theorem. In ocean waves, surface tension effects are negligible for wavelengths above a few decimetres. 

As the waves propagate, their energy is transported. The energy transport velocity is the group velocity. As a result, the wave energy flux, through a vertical plane of unit width perpendicular to the wave propagation direction, is equal to:

${\displaystyle P=E\,c_{g},\,\ }$

with c_g the group velocity (m/s). Due to the dispersion relation for water waves under the action of gravity, the group velocity depends on the wavelength λ, or equivalently, on the wave period T. Further, the dispersion relation is a function of the water depth h. As a result, the group velocity behaves differently in the limits of deep and shallow water, and at intermediate depths:

Deep-water characteristics and opportunities

Deep water corresponds with a water depth larger than half the wavelength, which is the common situation in the sea and ocean. In deep water, longer-period waves propagate faster and transport their energy faster. The deep-water group velocity is half the phase velocity. In shallow water, for wavelengths larger than about twenty times the water depth, as found quite often near the coast, the group velocity is equal to the phase velocity.

History

The first known patent to use energy from ocean waves dates back to 1799, and was filed in Paris by Girard and his son. An early application of wave power was a device constructed around 1910 by Bochaux-Praceique to light and power his house at Royan, near Bordeaux in France. It appears that this was the first oscillating water-column type of wave-energy device. From 1855 to 1973 there were already 340 patents filed in the UK alone.

Modern scientific pursuit of wave energy was pioneered by Yoshio Masuda's experiments in the 1940s. He tested various concepts of wave-energy devices at sea, with several hundred units used to power navigation lights. Among these was the concept of extracting power from the angular motion at the joints of an articulated raft, which was proposed in the 1950s by Masuda.

A renewed interest in wave energy was motivated by the oil crisis in 1973. A number of university researchers re-examined the potential to generate energy from ocean waves, among whom notably were Stephen Salter from the University of Edinburgh, Kjell Budal and Johannes Falnes from Norwegian Institute of Technology (now merged into Norwegian University of Science and Technology), Michael E. McCormick from U.S. Naval Academy, David Evans from Bristol University, Michael French from University of Lancaster, Nick Newman and C. C. Mei from MIT. 

Stephen Salter's 1974 invention became known as Salter's duck or nodding duck, although it was officially referred to as the Edinburgh Duck. In small scale controlled tests, the Duck's curved cam-like body can stop 90% of wave motion and can convert 90% of that to electricity giving 81% efficiency.

In the 1980s, as the oil price went down, wave-energy funding was drastically reduced. Nevertheless, a few first-generation prototypes were tested at sea. More recently, following the issue of climate change, there is again a growing interest worldwide for renewable energy, including wave energy.

The world's first marine energy test facility was established in 2003 to kick-start the development of a wave and tidal energy industry in the UK. Based in Orkney, Scotland, the European Marine Energy Centre (EMEC) has supported the deployment of more wave and tidal energy devices than at any other single site in the world. EMEC provides a variety of test sites in real sea conditions. Its grid-connected wave test site is situated at Billia Croo, on the western edge of the Orkney mainland, and is subject to the full force of the Atlantic Ocean with seas as high as 19 metres recorded at the site. Wave energy developers currently testing at the centre include Aquamarine Power, Pelamis Wave Power, ScottishPower Renewables and Wello.

Modern technology

Wave power devices are generally categorized by the method used to capture or harness the energy of the waves, by location and by the power take-off system. Locations are shoreline, nearshore and offshore. Types of power take-off include: hydraulic ram, elastomeric hose pump, pump-to-shore, hydroelectric turbine, air turbine, and linear electrical generator. When evaluating wave energy as a technology type, it is important to distinguish between the four most common approaches: point absorber buoys, surface attenuators, oscillating water columns, and overtopping devices.

Generic wave energy concepts: 1. Point absorber, 2. Attenuator, 3. Oscillating wave surge converter, 4. Oscillating water column, 5. Overtopping device, 6. Submerged pressure differential

Point absorber buoy

This device floats on the surface of the water, held in place by cables connected to the seabed. The point-absorber is defined as having a device width much smaller than the incoming wavelength λ. A good point absorber has the same characteristics as a good wave-maker. The wave energy is absorbed by radiating a wave with destructive interference to the incoming waves. Buoys use the rise and fall of swells to generate electricity in various ways including directly via linear generators, or via generators driven by mechanical linear-to-rotary converters or hydraulic pumps. EMF generated by electrical transmission cables and acoustics of these devices may be a concern for marine organisms. The presence of the buoys may affect fish, marine mammals, and birds as potential minor collision risk and roosting sites. Potential also exists for entanglement in mooring lines. Energy removed from the waves may also affect the shoreline, resulting in a recommendation that sites remain a considerable distance from the shore.

Surface attenuator

These devices act similarly to point absorber buoys, with multiple floating segments connected to one another and are oriented perpendicular to incoming waves. A flexing motion is created by swells that drive hydraulic pumps to generate electricity. Environmental effects are similar to those of point absorber buoys, with an additional concern that organisms could be pinched in the joints.

Oscillating wave surge converter

These devices typically have one end fixed to a structure or the seabed while the other end is free to move. Energy is collected from the relative motion of the body compared to the fixed point. Oscillating wave surge converters often come in the form of floats, flaps, or membranes. Environmental concerns include minor risk of collision, artificial reefing near the fixed point, EMF effects from subsea cables, and energy removal effecting sediment transport. Some of these designs incorporate parabolic reflectors as a means of increasing the wave energy at the point of capture. These capture systems use the rise and fall motion of waves to capture energy. Once the wave energy is captured at a wave source, power must be carried to the point of use or to a connection to the electrical grid by transmission power cables.

Oscillating water column

Oscillating Water Column devices can be located on shore or in deeper waters offshore. With an air chamber integrated into the device, swells compress air in the chambers forcing air through an air turbine to create electricity. Significant noise is produced as air is pushed through the turbines, potentially affecting birds and other marine organisms within the vicinity of the device. There is also concern about marine organisms getting trapped or entangled within the air chambers.

Overtopping device

Overtopping devices are long structures that use wave velocity to fill a reservoir to a greater water level than the surrounding ocean. The potential energy in the reservoir height is then captured with low-head turbines. Devices can be either on shore or floating offshore. Floating devices will have environmental concerns about the mooring system affecting benthic organisms, organisms becoming entangled, or EMF effects produced from subsea cables. There is also some concern regarding low levels of turbine noise and wave energy removal affecting the nearfield habitat.

Submerged pressure differential

Submerged pressure differential based converters are a comparatively newer technology utilizing flexible (usually reinforced rubber) membranes to extract wave energy. These converters use the difference in pressure at different locations below a wave to produce a pressure difference within a closed power take-off fluid system. This pressure difference is usually used to produce flow, which drives a turbine and electrical generator. Submerged pressure differential converters frequently use flexible membranes as the working surface between the ocean and the power take-off system. Membranes offer the advantage over rigid structures of being compliant and low mass, which can produce more direct coupling with the wave’s energy. Their compliant nature also allows for large changes in the geometry of the working surface, which can be used to tune the response of the converter for specific wave conditions and to protect it from excessive loads in extreme conditions.

A submerged converter may be positioned either on the sea floor or in midwater. In both cases, the converter is protected from water impact loads which can occur at the free surface. Wave loads also diminish in non-linear proportion to the distance below the free surface. This means that by optimizing the depth of submergence for such a converter, a compromise between protection from extreme loads and access to wave energy can be found. Submerged WECs also have the potential to reduce the impact on marine amenity and navigation, as they are not at the surface. Examples of submerged pressure differential converters include M3 Wave, Bombora Wave Power's mWave, and CalWave.

Environmental effects

Common environmental concerns associated with marine energy developments include:

• The risk of marine mammals and fish being struck by tidal turbine blades;
• The effects of EMF and underwater noise emitted from operating marine energy devices;
• The physical presence of marine energy projects and their potential to alter the behavior of marine mammals, fish, and seabirds with attraction or avoidance;
• The potential effect on nearfield and farfield marine environment and processes such as sediment transport and water quality.

The Tethys database provides access to scientific literature and general information on the potential environmental effects of wave energy.

Potential

The worldwide resource of coastal wave energy has been estimated to be greater than 2 TW. Locations with the most potential for wave power include the western seaboard of Europe, the northern coast of the UK, and the Pacific coastlines of North and South America, Southern Africa, Australia, and New Zealand. The north and south temperate zones have the best sites for capturing wave power. The prevailing westerlies in these zones blow strongest in winter. 

Estimates have been made by the National Renewable Energy Laboratory (NREL) for various nations around the world in regards to the amount of energy that could be generated from wave energy converters (WECs) on their coastlines. For the United States in particular, it is estimated that the total energy amount that could be generated along its coastlines is equivalent to ${\displaystyle 1170{\frac {Twh}{yr}}}$, which would account for nearly 33% of the total amount of energy consumed annually by the United States. While this sounds promising, the coastline along Alaska accounted for approx. 50% of the total energy created within this estimate. Considering this, there would need to be the proper infrastructure in place to transfer this energy from Alaskan shorelines to the mainland United States in order to properly capitalize on meeting United States energy demands. However, these numbers show the great potential these technologies have if they are implemented on a global scale to satisfy the search for sources of renewable energy. 

WECs have gone under heavy examination through research, especially relating to their efficiencies and the transport of the energy they generate. NREL has shown that these WECs can have efficiencies near 50%. This is a phenomenal efficiency rating among renewable energy production. For comparison, efficiencies above 10% in solar panels are considered viable for sustainable energy production. Thus, a value of 50% efficiency for a renewable energy source is extremely viable for future development of renewable energy sources to be implemented across the world. Additionally, research has been conducted examining smaller WECs and their viability, especially relating to power output. One piece of research showed great potential with small devices, reminiscent of buoys, capable of generating upwards of ${\displaystyle 6W}$of power in various wave conditions and oscillations and device size (up to a roughly cylindrical 21 kg buoy). Even further research has led to development of smaller, compact versions of current WECs that could produce the same amount of energy while using roughly one-half of the area necessary as current devices.

  

World wave energy resource map

Challenges

There is a potential impact on the marine environment. Noise pollution, for example, could have negative impact if not monitored, although the noise and visible impact of each design vary greatly.^[8] Other biophysical impacts (flora and fauna, sediment regimes and water column structure and flows) of scaling up the technology are being studied. In terms of socio-economic challenges, wave farms can result in the displacement of commercial and recreational fishermen from productive fishing grounds, can change the pattern of beach sand nourishment, and may represent hazards to safe navigation. Waves generate about 2,700 gigawatts of power. Of those 2,700 gigawatts, only about 500 gigawatts can be captured with current technology. Since 2008, Seabased Industry AB (SIAB) has deployed several units of wave energy converters (WECs) manufactured with different designs. Offshore deployments of WECs and underswater substation are being complicated procedures. SIAB discussed these deployments in terms of economy and time efficiency, as well as safety. Certain solutions are suggested for the various problems encountered during the deployments. It is found that the offshore deployment process can be optimized in terms of cost, time efficiency and safety.

Wave farms

A group of wave energy devices deployed in the same location is called wave farm, wave power farm or wave energy park. Wave farms represent a solution to achieve larger electricity production. The devices of a park are going to interact with each other hydrodynamically and electrically, according to the number of machines, the distance among them, the geometric layout, the wave climate, the local geometry, the control strategies. The design process of a wave energy farm is a multi-optimization problem with the aim to get a high power production and low costs and power fluctuations.

Wave farm projects

United Kingdom

• The Islay LIMPET was installed and connected to the National Grid in 2000 and is the world's first commercial wave power installation
• Funding for a 3 MW wave farm in Scotland was announced on February 20, 2007, by the Scottish Executive, at a cost of over 4 million pounds, as part of a £13 million funding package for marine power in Scotland. The first machine was launched in May 2010.
• A facility known as Wave hub has been constructed off the north coast of Cornwall, England, to facilitate wave energy development. The Wave hub will act as giant extension cable, allowing arrays of wave energy generating devices to be connected to the electricity grid. The Wave hub will initially allow 20 MW of capacity to be connected, with potential expansion to 40 MW. Four device manufacturers have so far expressed interest in connecting to the Wave hub. The scientists have calculated that wave energy gathered at Wave Hub will be enough to power up to 7,500 households. The site has the potential to save greenhouse gas emissions of about 300,000 tons of carbon dioxide in the next 25 years.
• A 2017 study by Strathclyde University and Imperial College focused on the failure to develop "market ready" wave energy devices – despite a UK government push of over £200 million in the preceding 15 years – and how to improve the effectiveness of future government support.

Portugal

• The Aguçadoura Wave Farm was the world's first wave farm. It was located 5 km (3 mi) offshore near Póvoa de Varzim, north of Porto, Portugal. The farm was designed to use three Pelamis wave energy converters to convert the motion of the ocean surface waves into electricity, totalling to 2.25 MW in total installed capacity. The farm first generated electricity in July 2008 and was officially opened on September 23, 2008, by the Portuguese Minister of Economy. The wave farm was shut down two months after the official opening in November 2008 as a result of the financial collapse of Babcock & Brown due to the global economic crisis. The machines were off-site at this time due to technical problems, and although resolved have not returned to site and were subsequently scrapped in 2011 as the technology had moved on to the P2 variant as supplied to E.ON and Scottish Renewables. A second phase of the project planned to increase the installed capacity to 21 MW using a further 25 Pelamis machines is in doubt following Babcock's financial collapse.

Australia

• Bombora Wave Power is based in Perth, Western Australia and is currently developing the mWave flexible membrane converter. Bombora is currently preparing for a commercial pilot project in Peniche, Portugal.
• A CETO wave farm off the coast of Western Australia has been operating to prove commercial viability and, after preliminary environmental approval, underwent further development. In early 2015 a $100 million, multi megawatt system was connected to the grid, with all the electricity being bought to power HMAS Stirling naval base. Two fully submerged buoys which are anchored to the seabed, transmit the energy from the ocean swell through hydraulic pressure onshore; to drive a generator for electricity, and also to produce fresh water. As of 2015 a third buoy is planned for installation.^[
• Ocean Power Technologies (OPT Australasia Pty Ltd) is developing a wave farm connected to the grid near Portland, Victoria through a 19 MW wave power station. The project has received an AU $66.46 million grant from the Federal Government of Australia.
• Oceanlinx will deploy a commercial scale demonstrator off the coast of South Australia at Port MacDonnell before the end of 2013. This device, the greenWAVE, has a rated electrical capacity of 1MW. This project has been supported by ARENA through the Emerging Renewables Program. The greenWAVE device is a bottom standing gravity structure, that does not require anchoring or seabed preparation and with no moving parts below the surface of the water.

United States

• Reedsport, Oregon – a commercial wave park on the west coast of the United States located 2.5 miles offshore near Reedsport, Oregon. The first phase of this project is for ten PB150 PowerBuoys, or 1.5 megawatts. The Reedsport wave farm was scheduled for installation spring 2013. In 2013, the project had ground to a halt because of legal and technical problems.
• Kaneohe Bay Oahu, Hawaii - Navy’s Wave Energy Test Site (WETS) currently testing the Azura wave power device. The Azura wave power device is 45-ton wave energy converter located at a depth of 30 (98 ft) in Kaneohe Bay.

Patents

• WIPO patent application WO2016032360 — 2016 Pumped-storage system – "Pressure buffering hydro power" patent application
• U.S. Patent 8,806,865 — 2011 Ocean wave energy harnessing device – Pelamis/Salter's Duck Hybrid patent
• U.S. Patent 3,928,967 — 1974 Apparatus and method of extracting wave energy – The original "Salter's Duck" patent
• U.S. Patent 4,134,023 — 1977 Apparatus for use in the extraction of energy from waves on water – Salter's method for improving "duck" efficiency
• U.S. Patent 6,194,815 — 1999 Piezoelectric rotary electrical energy generator
• Wave energy converters utilizing pressure differences US 20040217597 A1 — 2004 Wave energy converters utilizing pressure differences

Carbon footprint

From Wikipedia, the free encyclopedia

A carbon footprint is historically defined as the total emissions caused by an individual, event, organization, or product, expressed as carbon dioxide equivalent. Greenhouse gases (GHGs), including carbon dioxide, can be emitted through land clearance and the production and consumption of food, fuels, manufactured goods, materials, wood, roads, buildings, transportation and other services.

In most cases, the total carbon footprint cannot be exactly calculated because of inadequate knowledge of and data about the complex interactions between contributing processes, including the influence of natural processes that store or release carbon dioxide. For this reason, Wright, Kemp, and Williams, have suggested to define the carbon footprint as: 

A measure of the total amount of carbon dioxide (CO₂) and methane (CH₄) emissions of a defined population, system or activity, considering all relevant sources, sinks and storage within the spatial and temporal boundary of the population, system or activity of interest. Calculated as carbon dioxide equivalent using the relevant 100-year global warming potential (GWP100).

 

Visual representation of carbon footprint.

 

Most of the carbon footprint emissions for the average U.S. household come from "indirect" sources, e.g. fuel burned to produce goods far away from the final consumer. These are distinguished from emissions which come from burning fuel directly in one's car or stove, commonly referred to as "direct" sources of the consumer's carbon footprint.

The concept name of the carbon footprint originates from ecological footprint, discussion, which was developed by William E. Rees and Mathis Wackernagel in the 1990s. This accounting approach compares how much people demand compared to what the planet can renew. This allows to assess the number of "earths" that would be required if everyone on the planet consumed resources at the same level as the person calculating their ecological footprint. The carbon Footprint is one part of the ecological footprint. The carbon part was popularized by a large campaign of BP in 2005. In 2007, carbon footprint was used as a measure of carbon emissions to develop the energy plan for City of Lynnwood, Washington. Carbon footprints are more focused than ecological footprints since they measure merely emissions of gases that cause climate change into the atmosphere.

Carbon footprint is one of a family of footprint indicators, which also includes water footprint and land footprint.

Measuring carbon footprints

An individual's, nation's, or organization's carbon footprint can be measured by undertaking a GHG emissions assessment, a life cycle assessment, or other calculative activities denoted as carbon accounting. Once the size of a carbon footprint is known, a strategy can be devised to reduce it, e.g. by technological developments, energy efficiency improvements, better process and product management, changed Green Public or Private Procurement (GPP), carbon capture, consumption strategies, carbon offsetting and others.

For calculating personal carbon footprints, several free online carbon footprint calculators exist, including a few supported by publicly available peer-reviewed data and calculations including the University of California, Berkeley's CoolClimate Network research consortium and CarbonStory.These websites ask you to answer more or less detailed questions about your diet, transportation choices, home size, shopping and recreational activities, usage of electricity, heating, and heavy appliances such as dryers and refrigerators, and so on. The website then estimates your carbon footprint based on your answers to these questions. A systematic literature review was conducted to objectively determine the best way to calculate individual/household carbon footprints. This review identified 13 calculation principles and subsequently used the same principles to evaluate the 15 most popular online carbon footprint calculators. A recent study’s results by Carnegie Mellon's Christopher Weber found that the calculation of carbon footprints for products is often filled with large uncertainties. The variables of owning electronic goods such as the production, shipment, and previous technology used to make that product, can make it difficult to create an accurate carbon footprint. It is important to question, and address the accuracy of Carbon Footprint techniques, especially due to its overwhelming popularity.

Calculating the carbon footprint of an industry, product, or service is a complex task, as stated earlier. One tool industry uses is Life-cycle assessment (LCA), where carbon footprint may be one of many factors taken into consideration when assessing a product or service. The International Organization for Standardization has a standard called ISO 14040:2006 that has the framework for conducting an LCA study. Another method is through the Greenhouse Gas Protocol, a set of standards for tracking GHG emissions.

It should also be noted that predicting the carbon footprint of a process is also possible through estimations using the above standards. By using Emission intensities/Carbon intensities and the estimated annual use of a fuel, chemical, or other inputs, the carbon footprint can be estimated while a process is being planned/designed.

Direct carbon emissions

Direct carbon emissions come from sources that are directly from the site that is producing a product. These emissions can also be referred to as scope 1 and scope 2 emissions. 

Scope 1 emissions are emissions that are directly emitted from the site of the process or service. An example for industry would be the emissions related to burning a fuel on site. On the individual level, emissions from personal vehicles or gas burning stoves would fall under scope 1. 

Scope 2 emissions are the other emissions related to purchased electricity, heat, and/or steam used on site. In the US, the EPA has broken down electricity emission factors by state.

Indirect carbon emissions

Indirect carbon emissions are emissions from sources upstream or downstream from the process being studied, also known as scope 3 emissions.

Examples of upstream, indirect carbon emissions may include:

• Transportation of materials/fuels
• Any energy used outside of the production facility
• Wastes produced outside of the production facility

Examples of downstream, indirect carbon emissions may include:

• Any end-of-life process or treatments
• Product and waste transportation
• Emissions associated with selling the product

Ways to reduce personal carbon footprint

The most common way to reduce the carbon footprint of humans is to Reduce, Reuse, Recycle, Refuse. 

This can also be done by using reusable items such as thermoses for daily coffee or plastic containers for water and other cold beverages rather than disposable ones. If that option isn't available, it is best to properly recycle the disposable items after use. When one household recycles at least half of their household waste, they can save 1.2 tons of carbon dioxide annually.

Another easy option is to drive less. By walking or biking to the destination rather than driving, not only is a person going to save money on gas, but they will be burning less fuel and releasing fewer emissions into the atmosphere. However, if walking is not an option, one can look into carpooling or mass transportation options in their area. 

Yet another option for reducing the carbon footprint of humans is to use less air conditioning and heating in the home. By adding insulation to the walls and attic of one's home, and installing weather stripping or caulking around doors and windows one can lower their heating costs more than 25 percent. Similarly, one can very inexpensively upgrade the "insulation" (clothing) worn by residents of the home. For example, it's estimated that wearing a base layer of long underwear (top and bottom) made from a lightweight, super insulating fabric like microfleece (aka Polartec®, Capilene®) can conserve as much body heat as a full set of clothing, allowing a person to remain warm with the thermostat lowered by over 5 °C. These measures all help because they reduce the amount of energy needed to heat and cool the house. One can also turn down the heat while sleeping at night or away during the day, and keep temperatures moderate at all times. Setting the thermostat just 2 degrees lower in winter and higher in summer could save about 1 ton of carbon dioxide each year.

Another option is to stop having children, or at any rate to have fewer of them! World population has increased from three billion to nine billion in fifty years. Each of those nine billion people generate their own carbon footprint, small or large. Can we really afford to carry on expanding world population? If you think we shouldn't, you could do your part by having fewer, or no, children. 

Choice of diet is a major influence on a person's carbon footprint. Animal sources of protein (especially red meat), rice (typically produced in high methane-emitting paddies), foods transported long distance and/or via fuel-inefficient transport (e.g., highly perishable produce flown long distance) and heavily processed and packaged foods are among the major contributors to a high carbon diet. Scientists at the University of Chicago have estimated "that the average American diet – which derives 28% of its calories from animal foods – is responsible for approximately one and a half more tonnes of greenhouse gasses – as CO
2 equivalents – per person, per year than a fully plant-based, or vegan, diet." Their calculations suggest that even replacing one third of the animal protein in the average American's diet with plant protein (e.g., beans, grains) can reduce the diet's carbon footprint by half a tonne. Exchanging two thirds of the animal protein with plant protein is roughly equivalent to switching from a Toyota Camry to a Prius. Finally, throwing food out not only adds its associated carbon emissions to a person or household's footprint, it adds the emissions of transporting the wasted food to the garbage dump and the emissions of food decomposition, mostly in the form of the highly potent greenhouse gas, methane. 

The carbon handprint movement emphasizes individual forms of carbon offsetting, like using more public transportation or planting trees in deforested regions, to reduce one's carbon footprint and increase their "handprint."

Centre for Environment Education (CEE), Ahmedabad, India - a Centre of Excellence in Environmental Education has played a leading role in global efforts at strengthening the role of education in sustainable development over the years. The Handprint concepts signifying positive action and commitment towards Sustainability was launched at one of CEE's conferences “The 4th International Conference on Environmental Education”, in Ahmedabad, in 2007. The Handprint is being used around the world to strengthen action towards fulfillment of the UN SDGs. 

A July 2017 study published in Environmental Research Letters argued that the most significant way individuals could mitigate their own carbon footprint is to have one less child (58.6 tonnes CO₂-equivalent per year), followed by living car-free (2.4 CO₂-equivalent per year), forgoing air travel (1.6 CO₂-equivalent per trans-Atlantic trip) and adopting a plant-based diet (0.8 CO₂-equivalent per year). The study also found that most government resources on climate change focus on actions that have a relatively modest effect on greenhouse gas emissions, and concludes that "a US family who chooses to have one fewer child would provide the same level of emissions reductions as 684 teenagers who choose to adopt comprehensive recycling for the rest of their lives".

SDG Handprint Lab

SDG Handprint Lab of Centre for Environment Education (CEE) is an initiative that involves university students in direct Handprint action towards SDGs and targets through a unique pedagogy that makes them understand the complex and transdisciplinary nature of sustainable development in the context of local area sustainability issues. The programme builds a platform for discussion, and creates conditions for their active engagement and using their skills and knowledge to conduct research and executing Handprint activities. Exploring the themes of the SDGs is an excellent way to get the students to link their education and skill with real life problems in the wider community and environment.

Ways to reduce industry's carbon footprint

A product, service, or company’s carbon footprint can be affected by several factors including, but not limited to:

• Energy sources
• Offsite electricity generation
• Materials

These factors can also change with location or industry. However, there are some general steps that can be taken to reduce carbon footprint on a larger scale. 

In 2016, the EIA reported that in the US electricity is responsible for roughly 37% of Carbon Dioxide emissions, making it a potential target for reductions. Possibly the cheapest way to do this is through energy efficiency improvements. The ACEEE reported that energy efficiency has the potential to save the US over 800 billion kWh per year, based on 2015 data. Some potential options to increase energy efficiency include, but are not limited to:

• Waste heat recovery systems
• Insulation for large buildings and combustion chambers
• Technology upgrades, ie different light sources, lower consumption machines

Carbon Footprints from energy consumption can be reduced through the development of alternative energy projects, such as solar and wind energy, which are renewable resources. 

Reforestation, the restocking of existing forests or woodlands that have previously been depleted, is an example of Carbon Offsetting, the counteracting of carbon dioxide emissions with an equivalent reduction of carbon dioxide in the atmosphere. Carbon offsetting can reduce a companies overall carbon footprint by offering a carbon credit. 

A life cycle or supply chain carbon footprint study can provide useful data which will help the business to identify specific and critical areas for improvement. By calculating or predicting a process’ carbon footprint high emissions areas can be identified and steps can be taken to reduce in those areas.

Schemes to reduce carbon emissions: Kyoto Protocol, carbon offsetting, and certificates

Carbon dioxide emissions into the atmosphere, and the emissions of other GHGs, are often associated with the burning of fossil fuels, like natural gas, crude oil and coal. While this is harmful to the environment, carbon offsets can be purchased in an attempt to make up for these harmful effects.

The Kyoto Protocol defines legally binding targets and timetables for cutting the GHG emissions of industrialized countries that ratified the Kyoto Protocol. Accordingly, from an economic or market perspective, one has to distinguish between a mandatory market and a voluntary market. Typical for both markets is the trade with emission certificates:

• Certified Emission Reduction (CER)
• Emission Reduction Unit (ERU)
• Verified Emission Reduction (VER)

Mandatory market mechanisms

To reach the goals defined in the Kyoto Protocol, with the least economical costs, the following flexible mechanisms were introduced for the mandatory market:

• Clean Development Mechanism (CDM)
• Joint Implementation (JI)
• Emissions trading

The CDM and JI mechanisms requirements for projects which create a supply of emission reduction instruments, while Emissions Trading allows those instruments to be sold on international markets.

- Projects which are compliant with the requirements of the CDM mechanism generate Certified Emissions Reductions (CERs).

- Projects which are compliant with the requirements of the JI mechanism generate Emission Reduction Units (ERUs).

The CERs and ERUs can then be sold through Emissions Trading. The demand for the CERs and ERUs being traded is driven by: 

- Shortfalls in national emission reduction obligations under the Kyoto Protocol.

- Shortfalls amongst entities obligated under local emissions reduction schemes. 

Nations which have failed to deliver their Kyoto emissions reductions obligations can enter Emissions Trading to purchase CERs and ERUs to cover their treaty shortfalls. Nations and groups of nations can also create local emission reduction schemes which place mandatory carbon dioxide emission targets on entities within their national boundaries. If the rules of a scheme allow, the obligated entities may be able to cover all or some of any reduction shortfalls by purchasing CERs and ERUs through Emissions Trading. While local emissions reduction schemes have no status under the Kyoto Protocol itself, they play a prominent role in creating the demand for CERs and ERUs, stimulating Emissions Trading and setting a market price for emissions.

A well-known mandatory local emissions trading scheme is the EU Emissions Trading Scheme (EU ETS). 

New changes are being made to the trading schemes. The EU Emissions Trading Scheme is set to make some new changes within the next year. The new changes will target the emissions produced by flight travel in and out of the European Union.

Other nations are scheduled to start participating in Emissions Trading Schemes within the next few year. These nations include China, India and the United States.

Voluntary market mechanisms

In contrast to the strict rules set out for the mandatory market, the voluntary market provides companies with different options to acquire emissions reductions. A solution, comparable with those developed for the mandatory market, has been developed for the voluntary market, the Verified Emission Reductions (VER). This measure has the great advantage that the projects/activities are managed according to the quality standards set out for CDM/JI projects but the certificates provided are not registered by the governments of the host countries or the Executive Board of the UNO. As such, high quality VERs can be acquired at lower costs for the same project quality. However, at present VERs can not be used in the mandatory market.

The voluntary market in North America is divided between members of the Chicago Climate Exchange and the Over The Counter (OTC) market. The Chicago Climate Exchange is a voluntary yet legally binding cap-and-trade emission scheme whereby members commit to the capped emission reductions and must purchase allowances from other members or offset excess emissions. The OTC market does not involve a legally binding scheme and a wide array of buyers from the public and private spheres, as well as special events that want to go carbon neutral. Being carbon neutral refers to achieving net zero carbon emissions by balancing a measured amount of carbon released with an equivalent amount sequestered or offset, or buying enough carbon credits to make up the difference.

There are project developers, wholesalers, brokers, and retailers, as well as carbon funds, in the voluntary market. Some businesses and nonprofits in the voluntary market encompass more than just one of the activities listed above. A report by Ecosystem Marketplace shows that carbon offset prices increase as it moves along the supply chain—from project developer to retailer.

While some mandatory emission reduction schemes exclude forest projects, these projects flourish in the voluntary markets. A major criticism concerns the imprecise nature of GHG sequestration quantification methodologies for forestry projects. However, others note the community co-benefits that forestry projects foster. Project types in the voluntary market range from avoided deforestation, afforestation/reforestation, industrial gas sequestration, increased energy efficiency, fuel switching, methane capture from coal plants and livestock, and even renewable energy. Renewable Energy Certificates (RECs) sold on the voluntary market are quite controversial due to additionality concerns. Industrial Gas projects receive criticism because such projects only apply to large industrial plants that already have high fixed costs. Siphoning off industrial gas for sequestration is considered picking the low hanging fruit; which is why credits generated from industrial gas projects are the cheapest in the voluntary market.

The size and activity of the voluntary carbon market is difficult to measure. The most comprehensive report on the voluntary carbon markets to date was released by Ecosystem Marketplace and New Carbon Finance in July 2007.

ÆON of Japan is firstly approved by Japanese authority to indicate carbon footprint on three private brand goods in October 2009.

Average carbon footprint per person by country

According to The World Bank, the global average carbon footprint in 2014 was 4.97 metric tons CO₂/cap. The EU average for 2007 was about 13.8 tons CO₂e/cap, whereas for the U.S., Luxembourg and Australia it was over 25 tons CO₂e/cap. In 2017, the average for the USA was about 20 metric tons CO₂e.

Mobility (driving, flying & small amount from public transit), shelter (electricity, heating, construction) and food are the most important consumption categories determining the carbon footprint of a person. In the EU, the carbon footprint of mobility is evenly split between direct emissions (e.g. from driving private cars) and emissions embodied in purchased products related to mobility (air transport service, emissions occurring during the production of cars and during the extraction of fuel).

The carbon footprint of U.S. households is about 5 times greater than the global average. For most U.S. households the single most important action to reduce their carbon footprint is driving less or switching to a more efficient vehicle.

The carbon footprints of energy

The following table compares, from peer-reviewed studies of full life cycle emissions and from various other studies, the carbon footprint of various forms of energy generation: nuclear, hydro, coal, gas, solar cell, peat and wind generation technology. 

The Vattenfall study found renewable and nuclear generation responsible for far less CO
2 than fossil fuel generation.

 

Emission factors of common fuels

Fuel/ resource		Thermal (g[CO2-eq]/MJth)	Energy intensity (Jth/Je)	Electric (g[CO2-eq]/kW·he)
Coal	B	91.50–91.72	2.62–2.85	863–941
	Br	94.33	3.46	1,175
		88	3.01	955
Oil		73	3.40	893
Natural gas	cc	68.20	−	577
	oc	68.4		751
				599
Geothermal power	TL	3~	−	0–1
	TW			91–122
Uranium Nuclear power	WL	N/A	0.18	60
	WL		0.20	65
Hydroelectricity (run of river)		N/A	0.046	15
Conc. solar power				40±15
Photovoltaics			0.33	106
Wind power			0.066	21

Note: 3.6 megajoules (MJ) = 1 kilowatt-hour (kW·h), thus 1 g/MJ = 3.6 g/kW·h.

B

Black coal (supercritical)–(new subcritical)

Br

Brown coal (new subcritical)

cc

combined cycle

oc

open cycle

T_L

Low-temperature/closed-circuit (geothermal doublet)

T_H

High-temperature/open-circuit

W_L

Light water reactors

W_H

Heavy water reactors, estimate.

These three studies thus concluded that hydroelectric, wind, and nuclear power produced the least CO₂ per kilowatt-hour of any other electricity sources. These figures do not allow for emissions due to accidents or terrorism. Wind power and solar power, emit no carbon from the operation, but do leave a footprint during construction phase and maintenance during operation. Hydropower from reservoirs also has large footprints from initial removal of vegetation and ongoing methane (stream detritus decays anaerobically to methane in bottom of reservoir, rather than aerobically to CO₂ if it had stayed in an unrestricted stream).

The table above gives the carbon footprint per kilowatt-hour of electricity generated, which is about half the world's man-made CO₂ output. The CO₂ footprint for heat is equally significant and research shows that using waste heat from power generation in combined heat and power district heating, chp/dh has the lowest carbon footprint, much lower than micro-power or heat pumps.

Coal production has been refined to greatly reduce carbon emissions; since the 1980s, the amount of energy used to produce a ton of steel has decreased by 50%.

Passenger transport

Average carbon dioxide emissions (grams) per passenger mile (USA). Based on 'Updated Comparison of Energy Use & CO
2 Emissions From Different Transportation Modes, October 2008' (Manchester, NH: M.J. Bradley & Associates, 2008), p. 4, table 1.1

 

This section gives representative figures for the carbon footprint of the fuel burned by different transport types (not including the carbon footprints of the vehicles or related infrastructure themselves). The precise figures vary according to a wide range of factors.

Flight

Some representative figures for CO₂ emissions are provided by LIPASTO's survey of average direct emissions (not accounting for high-altitude radiative effects) of airliners expressed as CO₂ and CO₂ equivalent per passenger kilometre:

• Domestic, short distance, less than 463 km (288 mi): 257 g/km CO₂ or 259 g/km (14.7 oz/mile) CO₂e
• Long distance flights: 113 g/km CO₂ or 114 g/km (6.5 oz/mile) CO₂e

However, emissions per unit distance travelled is not necessarily the best indicator for the carbon footprint of air travel, because the distances covered are commonly longer than by other modes of travel. It is the total emissions for a trip that matters for a carbon footprint, not the merely rate of emissions. For example, a greatly more distant holiday destination may be chosen than if another mode of travel were used, because air travel makes the longer distance feasible in the limited time available.

Road

CO₂ emissions per passenger-kilometre (pkm) for all road travel for 2011 in Europe as provided by the European Environment Agency:

• 109 g/km CO₂ (Figure 2)

For vehicles, average figures for CO₂ emissions per kilometer for road travel for 2013 in Europe, normalized to the NEDC test cycle, are provided by the International Council on Clean Transportation:

• Newly registered passenger cars: 127 g CO₂/km
• Hybrid-electric vehicles: 92 g CO₂/km
• Light commercial vehicles (LCV): 175 g CO₂/km

Average figures for the United States are provided by the US Environmental Protection Agency, based on the EPA Federal Test Procedure, for the following categories:

• Passenger cars: 200 g CO₂/km (322 g/mi)
• Trucks: 280 g CO₂/km (450 g/mi)
• Combined: 229 g CO₂/km (369 g/mi)

Rail

In 2005, the US company Amtrak's carbon dioxide equivalent emissions per passenger kilometre were 0.116 kg, about twice as high as the UK rail average (where much more of the system is electrified), and about eight times a Finnish electric intercity train.

Sea

Average carbon dioxide emissions by ferries per passenger-kilometre seem to be 0.12 kg (4.2 oz). However, 18-knot ferries between Finland and Sweden produce 0.221 kg (7.8 oz) of CO₂, with total emissions equalling a CO₂ equivalent of 0.223 kg (7.9 oz), while 24–27-knot ferries between Finland and Estonia produce 0.396 kg (14.0 oz) of CO₂ with total emissions equalling a CO₂ equivalent of 0.4 kg (14 oz).

The carbon footprints of products

Several organizations offer footprint calculators for public and corporate use, and several organizations have calculated carbon footprints of products. The US Environmental Protection Agency has addressed paper, plastic (candy wrappers), glass, cans, computers, carpet and tires. Australia has addressed lumber and other building materials. Academics in Australia, Korea and the US have addressed paved roads. Companies, nonprofits and academics have addressed mailing letters and packages. Carnegie Mellon University has estimated the CO₂ footprints of 46 large sectors of the economy in each of eight countries. Carnegie Mellon, Sweden and the Carbon Trust have addressed foods at home and in restaurants. 

The Carbon Trust has worked with UK manufacturers on foods, shirts and detergents, introducing a CO₂ label in March 2007. The label is intended to comply with a new British Publicly Available Specification (i.e. not a standard), PAS 2050, and is being actively piloted by The Carbon Trust and various industrial partners. As of August 2012 The Carbon Trust state they have measured 27,000 certifiable product carbon footprints.

Evaluating the package of some products is key to figuring out the carbon footprint. The key way to determine a carbon footprint is to look at the materials used to make the item. For example, a juice carton is made of an aseptic carton, a beer can is made of aluminum, and some water bottles either made of glass or plastic. The larger the size, the larger the footprint will be.

Food

In a 2014 study by Scarborough et al., the real-life diets of British people were surveyed and their dietary greenhouse gas footprints estimated. Average dietary greenhouse-gas emissions per day (in kilograms of carbon dioxide equivalent) were:

• 7.19 for high meat-eaters
• 5.63 for medium meat-eaters
• 4.67 for low meat-eaters
• 3.91 for fish-eaters
• 3.81 for vegetarians
• 2.89 for vegans

Textiles

The precise carbon footprint of different textiles varies considerably according to a wide range of factors. However, studies of textile production in Europe suggest the following carbon dioxide equivalent emissions footprints per kilo of textile at the point of purchase by a consumer:

• Cotton: 8
• Nylon: 5.43
• PET (e.g. synthetic fleece): 5.55
• Wool: 5.48

Accounting for durability and energy required to wash and dry textile products, synthetic fabrics generally have a substantially lower carbon footprint than natural ones.

Materials

The carbon footprint of materials (also known as embodied carbon) varies widely. The carbon footprint of many common materials can be found in the Inventory of Carbon & Energy database, the GREET databases and models, and LCA databases via openLCA Nexus.

Cement

Cement production and carbon footprint resulting from soil sealing was 8.0 Mg person⁻¹ of total per capita CO₂ emissions (Italy, year 2003); the balance between C loss due to soil sealing and C stocked in man-made infrastructures resulted in a net loss to the atmosphere, -0.6 Mg C ha⁻¹ y⁻¹.