How Much Crop Residue Can Leave the Field as Fuel? A Non-Additive Constraint Account for Maize Stover

Guides to removing crop residue for fuel commonly list what the soil needs, what erosion control needs and what livestock need, and add the three figures. That addition double-counts: the same tonne of residue left on the field maintains soil carbon and provides erosion cover at once. This paper builds the account correctly, with the soil requirements combined by their maximum rather than their sum, for stated maize stover production of 5.0 tonnes of dry matter per hectare alongside 3.3 tonnes of grain. Soil-carbon maintenance is stated to require 2.2 tonnes per hectare returned; erosion cover of 30 percent requires 1.5 tonnes per hectare present at planting, or 2.143 tonnes at harvest after a stated overwinter survival of 0.7; a stated fodder allocation takes 0.8 tonnes per hectare. The binding soil constraint is carbon, at 2.2 tonnes per hectare, by a narrow margin over cover. The removable quantity is 2.0 tonnes per hectare, a fraction 0.4 of production, representing 33138.8 MJ of fuel energy per hectare and 1104.6 days of cooking for one stated household: one hectare's removable residue cooks for about 3.026 household-years. The additive account, by contrast, returns a negative removable quantity of -0.143 tonnes per hectare and would forbid a removal the field can in fact sustain on the stated assumptions. This study is simulated, not measured. SIMULATED, NOT MEASURED.