Biochar from pyrolysis key to climate change mitigation: report

Combustion of fuels produced by pyrolysis at Mississippi State University

Biochar could solve a significant piece of the climate problem – 12 percent of CO2 emissions – according to a study published last week in Nature Communications.

The study estimated CO2 mitigation potential from sustainably-produced biochar that would not endanger – and could actually enhance – food security, habitat and soil conservation.

The authors conclude that turning biomass waste into biochar could be more effective in mitigating climate change than using it to produce biofuels, which could mitigate 10 percent of CO2 emissions compared to biochar’s 12 percent, although they note that the climate benefits of biofuel vs biochar can vary by region. It is also significant that the biochar production process allows the choice of diverting some of the syngas biomass carbon to biofuels, while sequestering the rest.

Biochar is produced through a process called pyrolysis: heating waste biomass at low temperatures with very little oxygen to produce a char. The biochar is a stable form of carbon that sequesters the CO2 that plant biomass would normally release when decomposing.

Besides helping fight climate change, biochar can also be used a soil amendment in programs to enrich soils lacking in nutrients for food production.

“Biochar is a winning climate strategy that policymakers need to start supporting now to start drawing down excess CO2 that is on the verge of pushing the climate system past the tipping point for irreversible climate changes,” said Durwood Zaelke, President of the Institute for Governance & Sustainable Development.

CO2, unlike other well mixed greenhouse gases, does not break down in the atmosphere. Its natural removal depends upon the absorption and eventual sequestration in the oceans or land as part of the natural carbon cycle. Approximately 65% of emitted CO2 is removed from the atmosphere within a hundred years through fast equalization with the oceans and biosphere.

The remainder stays trapped until drawn down through much slower processes with an additional 15-30% being removed over the next 5,000 years, and the remaining ~10% after 400,000 to a million years. This very long lifetime makes it essential to develop and deploy “climate negative” technologies, starting with biochar, to draw down CO2 on a timescale of decades to a century or less, to prevent irreversible and catastrophic climate impacts.

“Time is short – unfortunately, even with aggressive cuts in CO2 emissions, we will not see significant cooling for a very long time, likely centuries. To avoid rising temperatures pushing us beyond the tipping points for irreversible impacts, we need biochar and other carbon-negative strategies,” added Zaelke.

More on the story.

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