Life Cycle Assessment of Wood Chips for Biofuels Production
- Anthony Halog
- Binod Neupane
Replacing fossil fuels with biofuels is an important strategy promoted by oil consuming countries, notably the US. Biofuels is deemed important to mitigate climate change and address the issues pertaining to depleting petroleum resource stocks. The US government has plans to produce 36 billion gallons of bio-ethanol and is expected to replace 30 percent of fossil fuels by 2022. Out of the target production, 21 billion gallons of biofuels need to be cellulosic ethanol. In 2005, US produced 3.9 billion gallons of bioethanol which was mostly produced from corn. Current bioethanol production contributes about 2% to the total US transportation fuel consumption. To achieve this target, production should grow by at least ten times. Recent studies have shown that wood chips can supply about 14 million tons of hemicellulose annually, along with co-production of pulp. In relative terms, net GHG emissions using cellulosic ethanol can be reduced by 3 times than the net GHG emissions from corn-based bio-ethanol. Wood chips warrants in depth separate LCA study since most of the published biofuels studies have not considered this stage to be a potential major environmental impacts, which might affect the veracity of complete cradle to gate LCA results.
The objective of this research is to assess the potential environmental life cycle environmental impacts and resource consumptions in producing woodchips for biofuels production. This is from cradle to gate analysis (from trees to woodchips). The Eco-Indicator 99 based LCA method was employed to evaluate the potential environmental and resource depletion impacts. Emissions to air, water and land in wood chips production are assessed in different stages. Data used are primarily based on available literature and life cycle inventories databases (Eco- Invent 2.0 and Franklin-98). The functional unit used in this study is to produce one million BTU energy of bio-ethanol which is equivalent to 2.303 tons of wood chips needed. Our initial results show that seedling production and tree harvest stages contribute the highest amount of emissions from trees to wood chips. Data analysis revealed that fossil fuel consumption and respiratory inorganic effects have relatively the most significant impact to the environment.