Is Biomass, Biofuel, Bioenergy & Biogas Sustainable?

In the guide below, we discuss whether biomass, biofuel, bioenergy and biogas might be sustainable across several indicators.

 

Summary – Is Biomass, Biofuel, Bioenergy & Biogas Sustainable?

 

 

Sustainability Of Biomass, Biofuel, Bioenergy, & Biogas Over Different Sustainability Indicators

Scarcity

Biomass tends to be a non scarce resource – it can be grown, harvested, and re-grown

Comparatively, other energy sources like fossil fuels tend to form over very long time periods, and are considered as scarce resources

 

Use Of Resources & Inputs To Produce

There can be a range of resources required to produce dedicated biomass i.e. biomass grown on land specifically for the use of biomass applications.

There’s the agricultural land itself (agricultural land in itself is a scarce resource, that has an opportunity cost when it’s used for biomass over other land uses), along with water, energy/fuel, and also agricultural inputs like fertilizer and pesticides.

Comparatively, second generation biomass feedstock in the form of non edible biomass like residues and waste, might have a lower resource footprint, because they come from the production of other goods or products.

Additionally, third generation biomass feedstock like algae don’t require the agricultural land like first generation feedstock does, but may need resources like water and energy for production.

 

 

theguardian.com indicates that ‘… bioenergy is an inefficient use of land [and water]’

They go on to explain how it’s inefficient, and the yield is poor, to turn the energy stored in plants and biomass (from photosynthesis) into useable energy, instead of using this biomass for other uses like food for example

They reference research that suggests that there wouldn’t be enough plants in production to meet the world’s total energy demand in the future

They point out that solar converts sunlight to energy with greater efficiency and less water use than bioenergy, and provide stats that illustrate how solar PV systems can generate far more useable energy per hectare of land, and also how electric motors using solar as an energy source might be far more land efficient than internal combustion engines using biomass derived fuel

They also indicate that fertile agricultural land might better be used for ‘food, timber, and carbon storage’, as opposed to biomass production

 

Pollution

– Biogas

Biogas in particular might have the ability to contribute to pollution with the use of anaerobic biodigesters

 

From vox.com:

RNG [has] local air [pollution] and water impacts [that] are concentrated in vulnerable communities

RNG exacerbates air pollution problems [because it’s chemically identical to natural gas, and] it has all the same effects when leaked or combusted

[Renewable natural gas] is reliant on a steady supply of landfills and factory farms, which produce the very sort of pollution that electrification eliminates.

 

– Biofuels

Biofuels also emit air pollutants when they are burnt.

 

Biodiesel has significantly higher NOx emissions compared to ordinary diesel fuel because it has much more oxygen (forbes.com)

 

Ethanol and ethanol-gasoline mixtures burn cleaner and have higher octane levels than gasoline that does not contain ethanol, but they also have higher evaporative emissions [that contribute to ozone and smog air pollutants] from fuel tanks and dispensing equipment. Gasoline requires extra processing to reduce evaporative emissions before blending with ethanol (eia.gov)

 

From vox.com: ‘RNG is also produced by sources that are themselves big polluters [as] two biggest sources of biogas [in California] are landfills and manure from factory farms.’

 

[In terms of biodiesel] oxygen present in the biodiesel may improve combustion thereby reducing particulate emissions, carbon monoxide and hydrocarbon (azocleantech.com)

 

Greenhouse Gas Emissions

 

When biofuels are burned, they emit roughly the same the amount of CO2 per unit of energy as petroleum fuels (theconversation.com)

 

vox.com notes that:

[For the use of biomethane in buildings …]

[The carbon emissions from biomethane depend on the feedstock used and other circumstances, but it might not be as …] low-carbon as the industry claims

[RNG is methane, so when it’s burnt, it’s it emits GHGs like methane]

Anaerobic digesters also leak methane, at a rate of between 2 and 3 percent, adding to their lifecycle GHGs in a way that is rarely captured in models

… [But] Especially in a temperate climate like California, RNG is not a viable alternative for decarbonizing buildings

[At the very least, biogas isn’t renewable or eco friendly]

RNG could work in the background [of some regions] to lower the carbon intensity of natural gas

The sun and wind are healthier sources of energy [though] …

 

From vox.com:

[For transportation]

Switching from diesel to [biomethane i.e. renewable natural gas] RNG [negates climate benefits because of gas pipeline leakage rates]

Even if there were no leakage, the combustion of methane in a vehicle emits carbon dioxide, carbon monoxide, and nitrogen oxides.

 

azocleantech.com:

[Whether or not ethanol as a biofuel has lower emissions than gasoline depends on the feedstock used, and the production processes used]

[Ethanol can have lower CO2 emissions per litre compared to conventional gasoline if certain crops are used, and if] bagasse is used to provide power and heat …

[There’s other instances where ethanol might produce less CO2 per litre compared to gasoline as well]

 

… studies have found that clearing forests to grow biomass results in a carbon penalty that takes decades to recoup, so it is best if biomass is grown on previously cleared land, such as under-utilized farmland (nrel.gov)

 

Calculating Greenhouse Gas Emissions

There is a lot of debate and there can be differing conclusions presented by studies about the greenhouse gas emissions by biomass derived products like biofuels, bioenergy and biogas

A lot of it can come down to how emissions are calculated, and assumptions made in the calculations

The physicsworld.com guide listed in the ‘sources’ list at the bottom of this post does a good job of explaining how the differences in calculations and assumptions can change the carbon emissions footprint of biomass derived goods and products

 

From theguardian.com:

… burning biomass directly emits a bit more carbon dioxide than fossil fuels for the same amount of generated energy.

But most calculations claiming that bioenergy reduces greenhouse gas emissions relative to burning fossil fuels do not include the carbon dioxide released when biomass is burned. They exclude it based on the assumption that this release of carbon dioxide is matched and implicitly offset by the carbon dioxide absorbed by the plants growing the biomass

Yet if those plants were going to grow anyway, simply diverting them to bioenergy does not remove any additional carbon from the atmosphere and therefore does not offset the emissions from burning that biomass.

Furthermore, when natural forests are felled to generate bioenergy or to replace the farm fields that were diverted to growing biofuels, greenhouse gas emissions go up.

 

From physicsworld.com:

[In the UK, some biomass power plants have emitted more CO2 than coal plants they’ve replaced]

[But, the biomass used – waste and residue vs dedicated biomass, how it’s transported to biomass plants, and more]

[Additionally, calculations on carbon emissions rest on assumptions of whether carbon is recaptured immediately by new biomass growth, and also whether biomass that is burned would have release carbon dioxide naturally when it rots down in nature]

[Overall, the carbon debt payback time of different biomass feedstock types is hotly disputed – it can depend on variables in how biomass is grown and managed and eventually processed]

Combustion and processing efficiencies for wood are less than coal – [this means each megawatt hour of electricity produced by wood produces more CO2 than coal]

[Some reports go as far to say that bioenergy isn’t carbon neutral on a timeline that is quick enough to achieve climate change goals]

[There’s a combined heat and power generation plant in Denmark that pays back it’s carbon debt quicker, du to different feedstock, locally sourcing feedstock, and maximizing the energy produced]

[Some waste or residue feedstock is limited in supply compared to demand for power, so, other energy sources have to be used]

[Clearing forests also impacts the soil and the soil’s ability to store carbon and impact the carbon cycle]

[Paying back the carbon debt if it’s front loaded is an issue]

 

Differences Between Carbon Cycle For Biomass vs Fossil Fuel

A difference between biomass derived energy sources and fossil fuels is:

– Fossil fuels are mined from the ground. Burning fossil fuels takes carbon that was stored under ground and releases it into the atmosphere

– With biomass on the other hand, carbon dioxide starts in the atmosphere, is absorbed by biomass, and is then released again into the atmosphere when bioenergy sources are burnt. So, greenhouse gases are cycled back into the air, as opposed to taking it from the ground and adding more to the atmosphere

 

Also have to consider that when crops are grown as biomass, forests or grassland might have to be cleared, and more carbon can be released in their process than what biomass will sequester

 

Second & Third Generation Biomass

Could increase energy yield and decrease carbon footprint, as there’s no need to cultivate crops and organic matter

Present new possibilities, and benefits and drawback compared to edible food and crop biomass grown as dedicated biomass

 

Practical, Economic & Other Considerations

In this guide, we discuss other considerations relating to biomass, biofuels, bioenergy, and also biogas, such as cost, performance, and practical considerations.

 

 

Sources

1. https://www.vox.com/energy-and-environment/2020/2/14/21131109/california-natural-gas-renewable-socalgas

2. https://www.azocleantech.com/article.aspx?ArticleID=337

3. https://climate.mit.edu/ask-mit/why-arent-biofuels-more-prevalent

4. https://www.theguardian.com/environment/2015/jan/29/biofuels-are-not-the-green-alternative-to-fossil-fuels-they-are-sold-as

5. https://www.nrel.gov/research/re-biomass.html

6. https://physicsworld.com/a/biomass-energy-green-or-dirty/

7. https://www.forbes.com/sites/judeclemente/2015/06/17/why-biofuels-cant-replace-oil/?sh=4daad4c1f60f

8. https://www.eia.gov/energyexplained/biofuels/biofuels-and-the-environment.php

9. https://theconversation.com/biofuels-turn-out-to-be-a-climate-mistake-heres-why-64463

 

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