Bioenergy can slow climate change - but the window is closing

Bioenergy is derived from the use of materials produced by living organisms. It is considered to be more environmentally friendly than fossil fuels because it is sustainable and does not add any extra carbon dioxide to the atmosphere than would be added if the organism had been left to die and decay. Corn and sugar cane, for example, can be used to produce combustible materials such as pellets for fuel once the corn kernels and sugar have been removed. 

Although there have been debates about using land to grow crops for bioenergy at the expense of growing crops for human food, biofuels such as sustainably grown wood, ethanol from sugar cane and corn, and methane gas from decomposing manure, are all currently produced and used in various parts of the world. It is clear that biofuels provide a useful alternative to fossil fuels and could form part of a strategy for reducing dependence on petrochemicals while at the same time still producing enough energy to meet demand.

However, research led by scientists at the University of York has found that climate change is likely to reduce the availability of biomass for energy production because crop yields will decrease in future. The experts warn that as temperatures rise, the window of opportunity to maximize the use of biomass from plants, wood and waste as a renewable energy source and an alternative to petrochemicals will start closing.

“Biomass fuels and feedstocks offer a renewable source of energy and a viable alternative to petrochemicals, but the results of our study act as a stark warning about how climate change will put their availability at risk if we continue to allow global temperatures to rise,” said study co-author  Professor James Clark.

“There is a tipping point where climate change will severely impede our ability to mitigate against its worst effects. Biomass with carbon capture and storage, including the manufacture of bio-based chemicals, must be used now if we are to maximize its advantage.”

In the latest report by the Intergovernmental Panel on Climate Change (IPCC) and in many assessments of climate mitigation, bioenergy with carbon capture and storage (BECCS) has been highlighted as a crucial element of the strategy for meeting the target of 2 °C or 1.5 °C warming set out in the Paris Agreement. BECCS is a geo-engineering technique that, in addition to being an alternative for fossil fuel energy, stores carbon and prevents it from entering the atmosphere as carbon dioxide (CO₂). This makes it a negative emissions technology.

The IPPC has suggested that the potential range of negative emissions from BECCS is between 0 and 22 gigatons per year, but as of 2019 only five facilities around the world were actively using BECCS technologies. In total they were capturing approximately 1.5 million tons of CO₂ per year. 

The researchers found that if urgent action is not taken to reduce fossil fuels in favor of bioenergy and other renewables, climate change will decrease crop yields – reducing the availability of biomass in future. Declining food production is also likely to lead people to clear natural landscapes in favor of croplands, which will further increase greenhouse gas emissions from land use change and further accelerate the rate of climate change. 

For example, the modeling showed that when the implementation of large-scale BECCS technology is delayed from 2040 to 2060, the yields of agricultural residue for use in biomass technologies would be reduced and this would negatively impact the capacity of BECCS to be effective. The experts said that this would lead to an increase in global warming from 1.7 to 3.7°C by 2200, which would cause crops to be less productive, resulting in a decrease in global average daily crop calories per capita from 2.1 million calories to 1.5 million calories.

The researchers calculate that in this scenario, the scale of the food trade would need to increase by 80 percent from 2019 levels in order to avoid severe food shortages in many parts of the developing world worst affected by climate change. 

Professor Clark added: “If negative-carbon mitigation technologies relying on biomass could be widely deployed in the short term, there is still hope that we can alleviate global warming and a global food crisis.”

The study is published in the journal Nature.

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By Alison Bosman, Earth.com Staff Writer