The world produces hundreds of millions of tons of agricultural by-products every year that are considered “waste” - plant stalks & roots, leaves, nut shells, fruit waste and more.
A large part of these supposed waste can actually be converted to valuable products.
One of the valuable products that can be derived from plant waste is biogas or renewable natural gas, a gas with properties similar to LPG and CNG, and can be used as a fuel in household and commercial cooking, industrial heating and transport.
What are the key sustainability benefits?
Unused agricultural waste gets converted to CO2 if burnt on the fields or into methane if left to rot. Both CO2 and methane are greenhouse gases and thus converting these to renewable natural gas through closed loop processes can significantly reduce the net greenhouse emissions from these.
An equally important benefit is the economic benefit to the society in the form of higher incomes for the farmer community. What was earlier wasted and was considered a nuisance can today provide them with substantial increases in their overall incomes.
How does this work?
Most agricultural waste is in the form of what is called lignocellulosic material - that is, the cellulose is bound by lignin, a glue-like material.
In order to convert this into biogas, the cellulose needs to be first separated from lignin (in a process called pre-treatment). The cellulose is then treated in an anaerobic digester using methanogenic microorganisms to produce biogas. This biogas is then scrubbed and upgraded to renewable natural gas which can be stored in cylinders and sold. For optimal, C/N ratio, the agricultural waste can be co-digested with other organic wastes such as food waste, animal manure etc.
New Opportunities to Convert Biomass “Waste” to Renewable Methane and Green Hydrogen
These technologies allow for the conversion of dense, low-moisture organic material into valuable renewable gas and biochar, creating new opportunities to manage forests, agricultural waste and other hard-to-handle organic feedstocks