MIT: Processing waste biomass to reduce airborne emissions
To prepare fields for planting, farmers often burn corn stalks, rice husks, hay, straw and other waste left behind from the previous harvest. In many places, the practice creates huge seasonal clouds of smog, contributing to air pollution that the World Health Organisation said results in the death of seven million people globally each year.
Annually, $120 billion worth of crop and forest residues are burned in the open worldwide — a major waste of resources in an energy-starved world, said Kevin Kung SM ’13, PhD ’17. Kung is working to transform this waste biomass into marketable products — and capitalise on a billion-dollar global market — through his MIT spinoff company, Takachar.
Founded in 2015, Takachar develops small-scale, low-cost, portable equipment to convert waste biomass into solid fuel using a variety of thermochemical treatments, including one known as oxygen-lean torrefaction. The technology emerged from Kung’s PhD project in the lab of Ahmed Ghoniem, the Ronald C. Crane (1972) Professor of Mechanical Engineering at MIT.
Biomass fuels, including wood, peat and animal dung, are a major source of carbon emissions — but billions of people rely on such fuels for cooking, heating and other household needs. “Currently, burning biomass generates 10% of the primary energy used worldwide, and the process is used largely in rural, energy-poor communities. We’re not going to change that overnight. There are places with no other sources of energy,” Ghoniem said.
What Takachar’s technology provides is a way to use biomass more cleanly and efficiently by concentrating the fuel and eliminating contaminants such as moisture and dirt, thus creating a “clean-burning” fuel — one that generates less smoke. “In rural communities where biomass is used extensively as a primary energy source, torrefaction will address air pollution head-on,” Ghoniem said.
Thermochemical treatment densifies biomass at elevated temperatures, converting plant materials that are typically loose, wet and bulky into compact charcoal. Centralised processing plants exist, but collection and transportation present major barriers to utilisation, Kung said. Takachar’s solution moves processing into the field - to date, Takachar has worked with about 5,500 farmers to process 9,000 metric tons of crops.
Takachar estimated its technology has the potential to reduce carbon dioxide equivalent emissions by gigatons per year at scale. (“Carbon dioxide equivalent” is a measure used to gauge global warming potential.) In recognition, in 2021 Takachar won the first-ever Earthshot Prize in the clean air category, a £1 million prize funded by Prince William and Princess Kate’s Royal Foundation.