Biomass is the World’s Oldest Source of Energy
In climate science, biomass (biological matter) is any organic material that comes from plants, animals or vegetables, which is used for energy production (electricity or heat), or in industrial processes as raw materials for a range of energy products. 1
Biomass is a renewable energy source whose importance is increasing rapidly alongside the trend towards decarbonization and the replacement of fossil fuels with cleaner biofuels. Properly handled, biomass reduces greenhouse gas emissions significantly. For this reason alone, the use of biomass has already become an essential climate change mitigation strategy for nations around the world.
Biomass includes: wood, charcoal, wood waste, straw, and other crop residues, seaweed, yard clippings, waste from food crops (wheat straw, bagasse), organic fractions of municipal solid wastes, paper, food waste, animal manure, or human waste from sewage plants. It also includes purposely grown energy crops such as algae, miscanthus, switchgrass and others.
Biomass may be relatively new as a word, but it’s our oldest source of energy. People have been burning it (in the form of wood) to heat their homes and cook their food for thousands of years. More evenly distributed around the world than fossil fuels like coal, oil and natural gas, biomass has been described as the most important renewable energy source in the world. 2
- Biomass is the World’s Oldest Source of Energy
- What is the Chemical Composition of Biomass?
- What’s the Difference Between Biomass and Bioenergy?
- How is Biomass Energy Converted into a Usable Energy Source?
- What Are the Main Types of Biomass?
- Why Use Biomass?
- Can Biomass be Mixed with Fossil Fuels to Produce Energy?
- How Does Biomass Differ From Fossil Fuels in Respect of the Carbon Cycle?
- How Can Biomass Generate Electricity?
- How Much of the World’s Energy Comes From Biomass?
- How Much Electricity Comes From Biomass?
- How Green is Biomass? Is it Really Carbon Neutral?
- Science Versus Politics
- Theory Versus Practice
- Modern Biomass
- Biomass is Not Guaranteed to Be Carbon Neutral
What Are the Main Alternatives to Biomass?
The main renewable alternatives to biomass, are: hydropower (hydroelectricity), solar power, offshore and onshore wind power, and subterranean geothermal energy.
What is the Chemical Composition of Biomass?
Biomass contains stored chemical energy from the sun. Obtained initially by plants – the planet’s “primary producers” – through a process called photosynthesis, this energy passes through the food web from plants – including phytoplankton – into animals, including marine zooplankton. In order to extract this energy from biomass, the biological matter can be burned directly or, alternatively, turned into liquid biofuel or biogas that can be burned as fuels.
Biomass is carbon based and contains a variety of organic compounds whose constituents typically include: hydrogen, oxygen, nitrogen, sometimes magnesium, along with small quantities of other atoms, pigments (chlorophyll), alkaline substances and other materials.
Components of biomass (such as plants and waste streams from agriculture and the food industry) that can be isolated include fiber, carbohydrates, sugars, proteins, oils and lignin (a rigid plant compound).
Biomass can be separated into several types: Fresh biomass (leaves and grass), lignocellulosic biomass (wood, straw and grasses) and aquatic biomass (microalgae, seaweeds and other aquatic plants). Each of these types contains differing amounts and types of ingredients.
Lignocellulosic biomass, for example, is rich in lignin, a useful bio-based alternative to certain petroleum products. Aquatic biomass is rich in oils and proteins, which are interesting components for biofuels. Fresh biomass has significant potential in a wide variety of locations. 3
What’s the Difference Between Biomass and Bioenergy?
Bioenergy (biologically-based energy) is the renewable energy extracted from biomass (biological matter). It’s the power (biopower or bioheat) produced by burning biomass or biofuels.
Biomass is the organic residue from recently deceased plants and animals. Often, this energy source must be processed in some way to turn it into a usable fuel, such as wood pellets, charcoal, methane, or alcohol for use as motor fuel. The energy obtained from burning these forms of biomass is called bioenergy.
What is Biofuel?
Biofuel is a fuel that is produced from biomass (biological material). Examples include ethanol (from corn/sugarcane), biodiesel (from vegetable oils), green diesel (from algae/plants) and biogas (methane from animal waste and other sources).
What Are Biomass Feedstocks?
The phrase ‘biomass feedstocks’ refers to any biomass material (everything from wood pellets to sugar cane) which is used to produce energy.
What is Biopower?
Biopower refers to electricity generated from any form or combination of biomass feedstock.
What is Bioheat?
Bioheat describes heat from any form of biomass or bio-based feedstock.
What Does Biogenic Mean?
A biogenic substance is anything that comes from living beings. The term includes any parts, residues, secretions, or products of plants or animals.
How is Biomass Energy Converted into a Usable Energy Source?
There are three common ways to convert biomass energy into a usable energy source. You can burn it, decompose it or ferment it.
1. Burning/Thermal Conversion
We can burn biomass to produce steam for making electricity, or we can burn it in a furnace or boiler to provide heat for power plants, factories and homes. The most common biomass feedstocks used in thermal conversion are materials like wood waste, paper and municipal solid waste (MSW).
There are three specific forms of thermal conversion – torrefaction, pyrolysis, and gasification – which vary according to the oxygen supply and the temperature attained during the conversion. 4
Before biomass is burned, it is usually dried. The process is called torrefaction. During this process, biomass is heated to a temperature of between 200° and 320° Celsius (390° to 610° Fahrenheit), losing roughly 20 percent of its original mass, but retaining 90 percent of its energy. During torrefaction, the biomass dries and turns into a blackened material. Afterwards it is compressed into briquettes. This heating, drying and compaction gives the briquettes a much higher energy density so that it produces more heat.
During pyrolysis, the biomass feedstock is heated to a temperature of between 200° and 300° Celsius (390° to 570° Fahrenheit) without any oxygen being present. The process produces pyrolysis oil, a synthetic gas known as syngas, and a solid residue known as biochar. All of these components can be used for energy.
Pyrolysis oil, also known as biocrude or bio-oil, is a form of tar. It is usually burned to produce electricity. Research is also underway into converting pyrolysis oil into a renewable alternative to petroleum.
Syngas is equally versatile. It can be turned into fuel (synthetic natural gas) or into methane and used as a substitute for natural gas.
Biochar is a form of charcoal, a carbon-rich material that serves as a soil additive, where it leads to improved growth of biomass by as much as several hundred percent. 5
Biological matter can also be directly converted to energy by gasification. During this process, a biomass feedstock (usually municipal solid waste) is heated to a temperature of 700° Celsius (1,300° Fahrenheit) with a controlled amount of oxygen, which produces syngas (a mixture of carbon monoxide and hydrogen) and slag (a glassy, molten liquid). The syngas can be burned to produce heat or electricity, or processed into biofuel for cars. The slag can be used to make cement, or asphalt.
Gasification is also used to produce the hydrogen for Hydrogen Fuel Cells which are used to generate power and to fuel vehicles. According to an estimate by the U.S. Department of Energy, biomass has the potential to produce 40 million tons of hydrogen per year – sufficient to power 150 million vehicles. A debate continues, however, about whether this technology is sustainable or economically feasible. The energy, for example, needed to compress, package, and transport the hydrogen leaves little energy available for practical use.
When plants and animals die, their remains are broken down by decomposers (like bacteria and fungi). If this process takes place in the presence of oxygen, the decomposers emit carbon dioxide (CO2). If there is no oxygen present, methane is emitted. (Note: methane is pretty much the same as natural gas, the fossil fuel.) Various forms of waste – such as animal, human and municipal solid waste – are processed in special facilities in order to produce methane.
Fermentation is another natural process during which microorganisms (e.g. bacteria or yeasts like Saccharomyces cerevisiae) convert biomass into a usable fuel – in this case an alcohol known as “ethanol”. The most common biomass feedstocks are crops with a high starch and sugar content, such as corn, barley, sorghum, sugar beet and sugar cane.
What Are the Main Types of Biomass?
There are four main categories of biomass material.
- Wood and agricultural products
- Municipal solid waste (MSW)
- Landfill gas and biogas
- Liquid biofuels: ethanol and biodiesel
Wood and Agricultural Products
Wood is essentially waste wood. It includes wood chips, bark, sawdust and other waste materials from sawmills and lumber facilities. Used mainly to generate electricity, this category accounts for the largest amount of biomass.
Agricultural products – grown specifically for the purpose – are also used to produce bioenergy. In the USA, these include corn, and soybeans as well as switchgrass and willow; in Europe, sugar beet, rapeseed, wheat, and willow; in Brazil, palm oil and sugarcane; in Asia, miscanthus, palm oil, sorghum, cassava and jatropha.
Algae – commonly encountered as ‘seaweed’, has huge potential as a source of biomass energy – or so its supporters claim. To begin with, it produces energy through photosynthesis at a much faster rate than any other biofuel feedstock — up to 30 times faster than food crops. Furthermore, algae can be cultivated in ocean water, so it neither depletes freshwater resources, nor takes up valuable food-growing acreage. Although, like all plants, algae releases CO2 when burned, it can be farmed and replenished so that it maintains the closed carbon cycle – with net-zero emissions – but over a shorter time span due to its rapid rate of photosynthesis.
Algae is also said to require less space than other bioenergy crops. The U.S. Department of Energy estimates that it would only take approximately 38,850 square kilometers (less than half the size of the state of Maine) to grow enough algae to replace all petroleum-fuelled energy needs in the United States. Other assessments differ. “Assessment of algal biofuel resource potential in the United States with consideration of regional water stress.” 6
Algae may have enormous potential as an alternative energy source. However, several companies have tried to turn algae farming into a commercial idea, and failed.
Municipal Solid Waste
Municipal solid waste (MSW) contains any biogenic materials such as food waste, grass clippings, leaves, wood, paper, cardboard; non-biomass items such as plastics and other oil-based synthetic products; noncombustible items such as glass and metals; as well as a range of other types of trash.
In the United States, MSW is typically used to produce energy at specialized waste-to-energy plants. The U.S. Environmental Protection Agency (EPA) has strict environmental rules requiring waste-to-energy plants to check for air pollution, and to remove any pollutants with control devices such as scrubbers and electrostatic precipitators. In terms of energy value, one ton of rubbish contains the same heat energy as 500 pounds of coal. But half of this comes from non-biomass material, like plastics.
Landfill Gas and Biogas
Landfill gas and biogas comes from municipal solid waste landfills. They are created by three processes. Firstly, microbial decomposition of organic material, especially through methane-producing methanogenesis. Most biogas emanates from this anaerobic mechanism. Second, chemical reactions between a variety of other synthetic components. Third, the breakdown by evaporation of solvents and other chemical products.
Because gases produced by landfills are both valuable and sometimes hazardous, monitoring techniques have been developed. Flame ionization detectors can be used to measure methane levels as well as total VOC levels. Surface monitoring and sub-surface monitoring as well as monitoring of the ambient air is carried out. In the United States, the Clean Air Act of 1990, requires large landfills to install gas control systems, but as usual, enforcement is crucial.
Human waste (sewage) and livestock waste (manure) is processed more rapidly by placing it in high-temperature digesters, which make it decompose more quickly. The resulting methane gas is then captured and used as biofuel.
Biofuels are not as efficient as fossil fuel petroleum. So usually they are blended with petroleum fuels (gasoline and diesel fuel) to power vehicles efficiently, without the emissions of greenhouse gases (GHGs) associated with fossil fuels. The two most common biofuels are ethanol and biodiesel.
Ethanol is a renewable biofuel which is made by fermenting biomass feedstocks that are high in carbohydrates, such as sugar cane, wheat, or corn. The most common blend of ethanol is E10 (10 percent ethanol, 90 percent petroleum). One acre of corn can produce about 1,500 liters (400 gallons) of ethanol, although this acreage is then unavailable to grow food crops. In addition, the corn-for-ethanol growth cycle places an extra strain on the local ecosystem due to the lack of variation in planting, and the continuous use of pesticides.
Biodiesel is a renewable biofuel made by combining alcohol with vegetable oil, animal fat, or recycled cooking grease. It is used as a replacement for normal diesel in cars, trucks and marine engines. It is most often blended with petroleum diesel in ratios of 2 percent (referred to as B2), 5 percent (B5), or 20 percent (B20). Biodiesel blends are also used as a form of heating oil. Pure biodiesel (B100) is also used in many applications.
Why Use Biomass?
Three reasons. First, because the use of biomass to produce electricity (biopower), or the fuel for heating and transport, significantly reduces emissions of greenhouse gases like carbon dioxide. And in the short term it can be used in conjunction with other fossil fuels, like coal, in co-firing power plants, and blended with petroleum or diesel in motor engine fuels, in order to reduce emissions.
Second, because biomass causes less pollution than coal mining, fracking, oil drilling, causes far less damage to the biosphere, and has none of the long-term problems of nuclear energy in respect of the containment of hazardous waste. For more on this, see: Environmental Effects of Fossil Fuels.
Third, because biomass is both sustainable and conservationist in its recycling of waste products and is much better aligned with the carbon cycle that moves carbon dioxide through the atmosphere, hydrosphere and the lithosphere.
As we shall see, biomass is not without its problems, but these are minor compared to the benefits it offers. Besides, biomass often consists of residues and other waste products that might otherwise rot, releasing greenhouse gases including methane a heat-trapping gas 84 times more potent that CO2 over a 20-year period. 7
Can Biomass be Mixed with Fossil Fuels to Produce Energy?
Yes. Wood chips, wood pellets, and biomass briquettes are combined with coal to co-fire conventional electricity generating plants. Co-firing reduces the need to build new facilities for processing biomass, and reduces the need for complex carbon capture and storage in aging power plants. And because the power plant now burns less coal, less greenhouse gas is released into the atmosphere. The mixing of renewables with fossil fuels has been going on for decades. For example, ethanol is commonly mixed with gasoline at a ratio of 10 percent, and less often at 15 percent.
Co-firing and biofuel-blending is not an ideal long-term strategy but it meets the immediate need to make dramatic cuts in our GHG emissions, as laid out in the IPCC’s Special Report on Global Warming of 1.5°C (2018).
How Does Biomass Differ From Fossil Fuels in Respect of the Carbon Cycle?
Fast Carbon Cycle
Carbon dioxide is absorbed from the atmosphere by plants, during photosynthesis. If the plant is subsequently eaten by animals, the organic plant biomass is converted into organic animal biomass, but this changes nothing of any significance. Because ultimately, all plants and animals must die, in which case the organic biomass is usually either broken down into its basic chemical components by tiny decomposers, or burned.
If broken down, its carbon is released back into the atmosphere, either in the form of carbon dioxide (CO2) or methane (CH4), depending upon whether oxygen is present. If burned, the carbon is released into the atmosphere as CO2.
This is how the fast carbon cycle works and has worked ever since the first plant organisms appeared.
Slow Carbon Cycle
Fossil fuels, such as coal, oil and natural gas, also come from carbon-rich organic biomass, but this biomass died and was only partially broken down before being buried in sediments and lithified (fossilized), many millions of years ago. By being buried and absorbed into the rock, this carbon entered the ‘slow’ carbon cycle.
In other words, fossil fuels represent a long-term store of carbon that has remained untouched for a geological time span, until it was dug up in the last century or so.
But, just like plant biomass, fossil fuels release CO2 into the atmosphere when burned. The big difference between biomass and fossil fuel is one of time scale.
Biomass (like a tree, for instance) removes carbon from the atmosphere while it is growing, and releases it back again when it is burned. If handled properly (sustainably) the tree is harvested as part of a constantly replenished plantation. This maintains a closed carbon cycle with no overall increase in atmospheric carbon dioxide.
Contrast this with what happens when the massive long-term store of fossil fuel carbon is burned. In the space of a mere 250 years, much of the carbon accumulated over hundreds of millions of years is suddenly vented into the air as heat-trapping CO2. No wonder the greenhouse effect mechanism was overwhelmed and began the process of global warming.
How Can Biomass Generate Electricity?
Biomass generates electricity in a number of ways, but the most common is combustion – burning wood or agricultural waste to heat water and produce steam, which spins the turbines that generate electrical power. In some bioenergy plants, the excess steam is used to power on-site manufacturing processes, boosting the energy efficiency of biomass electricity generation to around 80 percent.
How Much of the World’s Energy Comes From Biomass?
Statistics for global consumption of renewable energy and biomass vary enormously for no obvious reason. According to the United Stations REN21 Report (2019), renewable energy contributes 18.1 percent to the world’s total energy consumption. This energy consumption is divided as 7.5 percent coming from traditional biomass (basically wood), 4.2 percent as heat energy (non-biomass), 1 percent biofuels for transport, 3.6 percent hydroelectricity and 2 percent electricity from a mix of wind, solar, biomass, geothermal, and ocean power. 8
However, according to the International Energy Agency, “bioenergy accounts for roughly one-tenth of world total primary energy”. 9 Note that bioenergy means energy obtained exclusively from biomass. 10 By contrast, Statista.com states that all forms of renewable energy combined contribute no more than 4 percent of global energy.
So, take your pick: biomass either supplies 7.5 percent, 10 percent or less than 4 percent of global energy.
Fortunately, US statistics are more precise. Renewables account for 11 percent of primary energy. Biomass alone accounts for just over 4.7 percent. 11
Whatever figure is used, it’s clear that in order to avail of the benefits of renewable energy we need to invest much more in renewable technologies in order to replace the old-style dirty energy from coal, oil and gas.
NOTE: In developing countries, the biomass that is burned is mainly wood – which is commonly used as fuel for cooking on indoor open fires – or crop stubble. Burning wood in this way causes significant indoor air pollution due to its emissions of tiny inhaleable particles of black carbon that penetrate deep into the lungs. Crop stubble burning is a key contributor to the Asian Brown Cloud that appears over large areas of India and Bangladesh during the dry winter months.
How Much Electricity Comes From Biomass?
According to the United Stations REN21 Report (2019), renewable energy contributes 26 percent to global electricity generation. But biomass alone contributes just 2.2 percent. 12
In the United States renewables account for 17.5 percent of all electrical power generated in 2019. Biomass alone, accounts for 1.4 percent. (Wood, 71.4 percent; landfill gas, 14.2 percent; municipal solid waste, 7.1 percent; other, 7.1 percent.) 13
How Green is Biomass? Is it Really Carbon Neutral?
Words like ‘Biomass’, ‘Biopower’, and ‘Bioheat’, sound a lot greener than ‘fossil fuels’. But what are the facts – is biomass as climate-friendly and environmentally safe as its supporters say? Is it really a form of sustainable energy? Let’s take a close look at traditional biomass, or wood, for example.
Wood burning produces higher CO2 emissions per unit of energy generated, than fossil fuels. According to one study, chimney emissions from burning wood for heat can be 30 percent higher than those of coal and 2.5 times greater than those of natural gas, per unit of generated energy. 14 And when incinerating wood for electricity, smokestack emissions can be 1.5 times those of coal (per MWh) and more than three times higher than those of natural gas.
Note also, that unregulated biomass burning in India continues to impact on air quality in cities throughout the region. The practice of burning crop stubble, for example, creates clouds of particulate matter, which mix with vehicle exhaust fumes and ground level ozone to produce photochemical smog, that blights so many cities in the region. For about the effects of these pollutants, see: Health Effects of Air Pollution.
It’s true that the CO2 captured by the trees planted to replace the harvested wood, may offset these emissions, if allowed. But it takes a long time to achieve this ‘carbon balance’.
One study, for example, analyzed a broad mix of forests and harvesting regimes, and discovered that most options had a carbon payback time of more than a century. 15 And if the trees are from first-growth forests, or from biomes like the Amazon Rainforest, or if the planted trees are not allowed to reach maturity, the much-touted carbon balance – or carbon neutrality – may never happen.
Unfortunately, as our climate crisis intensifies, we need to reduce our greenhouse gas emissions as rapidly as possible. The IPCC’s Special Report on Global Warming warned that to limit the rise in temperature to 1.5°C, we should aim to achieve net-zero emissions by around 2050. 16 So now is not the time to encourage an increase in atmospheric CO2 levels by burning wood. See also: Why Does A Half-Degree Rise in Temperature Make Such a Difference to the Planet?
Science Versus Politics
In 2012, a U.S. Environmental Protection Agency Science Advisory Board ruled that bioenergy (energy from biomass) is not inherently “carbon neutral” in the near term – a view which is shared by more than 90 leading U.S. scientists.
These scientific opinions contradict those of the US Environmental Protection Agency, who recently declared that burning wood will be deemed carbon neutral. 17
They also contradict the views of the EU, whose energy ministers, have also determined that wood is carbon neutral. EU figures show that about half of Europe’s renewable energy is now produced by burning wood.
In response, the European Academies Science Advisory Council (EASAC) wrote directly to the President of the European Commission Jean-Claude Juncker in January 2018, warning against the “flawed” notion that burning wood should be considered carbon neutral. (The EASAC is a body formed by the national science academies of the EU Member States, Norway and Switzerland, to enable them to collaborate with each other in offering independent scientific advice to EU policy-makers.)
The EASAC letter stated:
“The potentially very long payback periods for forest biomass raise important issues given the UNFCCC’s aspiration of limiting warming to 1.5 °C above preindustrial levels in order to ‘significantly reduce the risks and impacts of climate change’. On current trends, this may be exceeded in around a decade. Relying on forest biomass for the EU’s renewable energy, with its associated initial increase in atmospheric carbon dioxide levels, increases the risk of overshooting the 1.5°C target if payback periods are longer than this. The European Commission should consider the extent to which large scale forest biomass energy use is compatible with UNFCCC targets and whether a maximum allowable payback period should be set in its sustainability criteria.”
In reply, President of the European Commission informed EASAC that “bioenergy… is sourced largely from domestic forest residues and wood waste.” Well that sounds good. Who can complain about burning waste and leftover residues? Except, of course, there’s nowhere near enough ‘waste’ or ‘residues’.
Therefore, as demand for wood pellets in the EU has skyrocketed, it has triggered an increase in logging both in the southeastern United States and in the forests of eastern and central Europe. This includes “illegal logging” of old-growth forest in sensitive biomes, like the Carpathian Mountains of Romania and national reserves in Poland and Slovakia. 18
Meantime, in the southeastern United States, deforestation is now the order of the day as loggers rush to satisfy demand for wood pellets to fuel biomass energy plants in Europe and Japan, according to a report by the Natural Resources Defense Council, the Dogwood Alliance, and the Southern Environmental Law Center.
According to the report, mature hardwood forests in North Carolina, Virginia, and along the Gulf Coast are being clear-cut, with whole trees being trucked to processing mills and thence to Europe and elsewhere. 19 According to the United Nations, forested areas in the U.S. Southeast are suffering at four times the rate of those in the Amazon Basin. See also: Effects of Deforestation.
Theory Versus Practice
The EU insist that mandatory rules are in place to prevent whole trees from being cut down for bioenergy. But it’s no good having rules if no one enforces them. The EU says that bioenergy for heat and power must produce at least 80 percent fewer lifecycle GHG emissions, compared to fossil fuels to be eligible for public support. It’s hard to see how hacking down old-growth forests that have stood for centuries, is going to achieve the sustainability criteria served up by the EU.
The fact that wood needs to be handled properly in order to make it climate-friendly, doesn’t mean that all biomass is suspect. Far from it. There are many different forms and processes of biomass that are already causing a notable reduction in our carbon emissions, as well as our environmental pollution. Here are two brief examples:
Some waste landfills collect methane-rich landfill gas, process it to remove CO2, water vapor, and hydrogen sulfide, and then sell the methane. Other landfills utilize the methane gas to generate electricity. According to an estimate from the U.S. Energy Information Administration (EIA), about 270 billion cubic feet of landfill gas was collected at about 352 U.S. landfills in 2018, and burned to produce about 11 billion kilowatt hours (kWh) of electricity – about 0.3 percent of the annual U.S. electricity production.
Some innovative livestock farmers cover their manure holding ponds, or lagoons, so as to capture biogas emitted in the lagoons. The methane in the biogas is then burned to heat water and buildings, and as power for diesel-engine generators to produce electricity on the farm. In 2018, the EIA estimated that about 30 dairies and livestock operations in the United States generated a total of around 266 million kWh (or 0.3 billion kWh) of electricity from biogas. 20
Biomass is Not Guaranteed to Be Carbon Neutral
The real point is, putting the prefix bio- in front of a word is no guarantee of climate friendliness. It doesn’t mean that the thing is carbon neutral. Each biomass project needs to be evaluated on its merits, without any wishful thinking. And rules concerning sustainability need to be enforced.
For example, burning municipal solid waste (MSW), or garbage, in waste-to-energy plants can produce toxic air pollution – due to high concentrations of various heavy metals – which can be hazardous to people and the environment if they are not properly controlled. Printing inks, dyes, and ceramics, for example, may contain lead and cadmium. Furthermore, decomposition that occurs at both landfill sites and municipal solid waste sites, can emit methane, unless the decomposition process is carefully regulated.
The only safety net we have is the assurance that a body like the US Environmental Protection Agency has got the situation under control. Unfortunately, judging by the failure of the EPA to keep on top of methane emissions from the natural gas industry, there’s no reason to suppose that waste handlers will be scrutinized more effectively.
Finally, one major issue that is not going to go away, is competition for food. Growing crops for biofuels is controversial because the land, fertilizers, and energy for growing these energy crops could be used to grow food crops instead. For example, in several parts of the world, sizeable areas of forest and natural vegetation have been cut down to cultivate sugar cane for ethanol, and soybeans or oil palm trees for biodiesel. As global population nears 11 billion towards the end of the century, the competition for land between food growers and energy-crop farmers is likely to be intense.
- “EIA” U.S. Energy Information Administration.
- “Biofuels. Green Energy and Technology.” (2009) By Ayhan Demirbas. Springer, London.
- “The Potential of Biomass from Wood, Leaves, and Grass as Renewable Energy Sources in South Sumatera, Indonesia.” Nukman & Riman Sipahutar (2015) Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 37:24, 2710-2715
- “A Combined Overview of Combustion, Pyrolysis, and Gasification of Biomass.” Akhtar, A., Krepl, V., & Ivanova, T. (2018). Energy & Fuels 32(7), 7294–7318.
- “Biochar as a Renewable Energy Source.”
- Hui Xu, et al; Algal Research. Volume 37, January 2019, Pages 30-39.
- “Why Use Biomass?”
- UNEP REN21 Report.
- “Bioenergy.” International Energy Agency (IEA)
- “What is Bioenergy?”
- “U.S. primary energy consumption by energy source, 2019.”
- “Figure 8. Estimated Renewable Energy Share of Global Electricity Production.”
- “What is U.S. electricity generation by energy source?”
- “Range and uncertainties in estimating delays in greenhouse gas mitigation potential of forest bioenergy sourced from Canadian forests.” Jerome Laganiere, et al; 2015.
- “Carbon debt and carbon sequestration parity in forest bioenergy production.” Stephen R. Mitchell et al; 2012.
- IPCC’s Special Report on Global Warming of 1.5°C (2018): Summary for policymakers.
- “The EPA Declared That Burning Wood Is Carbon Neutral. It’s Actually a Lot More Complicated.”
- “Carbon Loophole: Why Is Wood Burning Counted as Green Energy?” Fred Pearce.
- “Global Markets for Biomass Energy are Devastating U.S. Forests.” NRDC Report. 2019
- “Landfill Gas & Biogas.”