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Photo of the Biofuels Cropping System Experiment in Michigan, taken by an unmanned aerial vehicle (UAV)

Biomass fuels made from grass could help mitigate global warming

Image credit: Ryan Mater

Biomass fuels derived from various grasses could significantly mitigate global warming by reducing carbon, a long-term field study has found.

The study, conducted by researchers at Ben-Gurion University of the Negev (BGU), Israel, and Michigan State University (MSU), USA, examined a number of different cellulosic biofuel crops to test their potential as a petroleum alternative in ethanol fuel and electric light-duty vehicles, including passenger cars and small trucks.

According to experts, climate change mitigation scenarios – limiting global temperature increases to 1.5°C – rely on decarbonising vehicle fuel with bioenergy production together with carbon capture and storage (BECCS).

Carbon capture and storage (CCS) refers to technology that can capture up to 90 per cent of the carbon dioxide (CO2) emitted during electricity generation and industrial processes. This prevents the atmospheric increase of CO2 concentration.

The researchers said, however, that using both CCS and renewable biomass is one of the few carbon abatement technologies resulting in a “carbon-negative” mode – removing carbon dioxide from the atmosphere.

For the first time, the research evaluates bioenergy feedstocks grown side-by-side. The seven crops in the investigation included switchgrass, giant miscanthus, poplar trees, maize residuals and restored native prairie. It also featured a combination of grasses and vegetation that grows spontaneously following field abandonment.

“Every crop we tested had a very significant mitigation capacity despite being grown on very different soils and under natural climate variability,” said Dr Ilya Gelfand of the BGU French Associates Institute for Agriculture and Biotechnology of Drylands.

“These crops could provide a very significant portion of the decarbonisation of US light-duty vehicle transport to curb CO2 emissions and slow global warming,” he explained, emphasising that, “decarbonisation of transportation is critical to limit rising temperatures”.

In the study, when compared with petroleum-only emissions, the researchers found that ethanol with bioenergy was 78-290 per cent in reducing carbon emissions, whereas ethanol was 204-416 per cent improved. Meanwhile, biomass powered electric vehicles powered by biomass was 74-303 per cent cleaner and biomass-powered electric vehicles combined with CSS was 329-558 per cent “superior”, the team said.

The investigation was conducted at Michigan State University’s (MSU) Kellogg Biological Station and the University of Wisconsin’s Arlington Research Station which is part of the US Department of Energy’s Great Lakes Bioenergy Research Center. The team said, however, that interestingly, the crops grown at MSU did as well as those grown at the more fertile Wisconsin site.

“This is significant because it means that we’re likely to be able to produce these crops on marginal lands and still get high productivity,” said Professor Phil Robertson of MSU. “Long-term field experiments that include weather extremes such as drought, and actual rather than estimated greenhouse gas emissions, are crucial for stress-testing models assumptions.”

In the next phase of the research, the team aim to assess other environmental and economic aspects of bioenergy crops. The best biofuel crops need to be “economically attractive” to farmers, don’t add more nitrogen or pesticides to the environment and are conservation-friendly, the researchers disclosed.

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