As crop straw and firewood are generated as by-products of food production systems, they are perceived to be sustainable energy sources that do not threaten food security by Chinese government for a long time. However, the time spent on collecting straw and firewood may create a burden on rural household, as it could reduce the available labor inputs for agricultural production, which in turn, possibly brings negative impact on food security. Building on an integrated agriculture-energy production system, a Symmetric Normalized Quadratic (SNQ) multi-output profit function (which includes labor allocations as quasi-fixed factors) is estimated to investigate the impacts of traditional biomass energy use on agricultural production in this paper.