Pyrolysis and gasification are considered as a means of producing renewable energy and improving energy sustainability, which has become attractive renewable technologies to many countries. Unlike other studies that are conducted in small scale, this study aims to aggregate the economic and environmental effects such as agricultural benefits, energy sale, and carbon sequestration to provide more detailed information to decision-makers before these projects are widely employed. This study first employs a lifecycle assessment to investigate the feasibility, profitability, and emission reduction of four major pyrolysis and gasification technologies using crop residuals, and then conducts a sensitive analysis to examine the most influential factors. The results indicate that the intermediate pyrolysis with rice straw and slow pyrolysis from corn stover could offset the carbon dioxide the most. However, the pyrolysis value is also sensitive to production of the feedstock used. Value adding of stover-based biochar under fast pyrolysis improves profitability but other technologies do not have such patterns. Additionally, while gasification can generate considerable amount of renewable electricity, it yields almost zero percent of biochar that can be used as a soil amendment, and thus its contribution to agricultural sector is trivial.

Mining and using depletable fossil fuel usually result in severe environmental problem such as climate change in the global scale and acid rain in the regional level. To improve sustainable development, it is important to substitute fossil fuel with renewable and clean energy sources. In this study we employ a partial equilibrium, price endogenous mathematical programming model to analyze how bioenergy development in Taiwan can (1) enhance domestic energy production, (2) reduce the carbon dioxide (CO 2) and sulfur dioxide (SO 2) emissions, and (3) protect the environment. The results show that the ethanol expands with an increase in gasoline price, but SO 2 emission reduction would shrink because of a reduction in renewable electricity generation. Conversely, up to 10.4% of Taiwan's annual SO 2 emission can be reduced in the face of higher coal and emission prices. A tradeoff between CO 2 and SO 2 emission reductions is perceived during the switch of production of liquid and nonliquid bioenergy. Policy implications such as technology selection, market operation, and government subsidy are also discussed.