Biomass residues (from agriculture, forestry, etc.) are mostly produced rural, dispersed settings. As such, it is often very expensive to transport these bulky, loose, and wet wastes over long distances to centralized processing facilities where they can be converted into energy or other useful products. It is estimated that more than $120 billion/year of biomass residues are being burned in the open, contributing to air pollution, urban smog, as well as greenhouse gas emissions. We decentralize the biomass conversion process. Imagine low-cost, small-scale, and portable biomass processing reactors that can be latched onto the back of tractors, donkey carts, and even shipping containers, and be deployed in a decentralized manner, and be transported from farm to farm where these reactors can enable the on-site conversion and upgrading of biomass residues. The underlying science that we utilize is called biomass torrefaction, which is a thermochemical treatment process. Unlike conventional biomass torrefaction reactors, which are often large-scale and capital-intensive, we utilize a new principle called oxygen-lean torrefaction to drastically downsize the scale and capital cost of biomass torrefaction. Our reactor units do not require external heat source to run itself, are resilient in resource-constrained settings, and are 100 times smaller in capital cost and scale compared to other existing torrefaction reactors.