Evaluating eutrophication potential of bioproducts using life cycle assessment methods

摘要

Reactive nutrients are accumulating rapidly in the environment due, in part, to increasing demand for food and energy products derived from agriculture. Recently, biobased fuels from renewable resources have gained high development priority due to national energy security policies and to their potential carbon emission reduction compared to their petroleum counterparts. However, biofuels from first generation feedstocks (e.g., corn and soybean) exhibit a significant environmental tradeoff in the form of increased water quality degradation (i.e. eutrophication and hypoxia). To mitigate eutrophication resulting from increased agricultural production, it is important 1) to identify eutrophication potential of the main bioproducts including biofuels and foods; and 2) to evaluate the effectiveness of possible mitigation strategies. Multiple strategies exist for reducing nutrient loading including optimizing farming practices and encouraging consumers to purchase low nutrient intensity bioproducts. This research quantified the life cycle nutrient flows and environmental impacts of foods and biofuels, and subsequently evaluated the mitigation potentials of management strategies.Research results show that different food groups exhibit highly variable nitrogen- intensity, on average, red meat and dairy products require much more nitrogen than cereals/carbohydrates. The ranking of foods' nitrogen footprints is not consistent with their carbon footprint. For example, dairy products and chicken/eggs have relatively high nitrogen footprint and low carbon footprints. The life cycle assessment of biodiesels in Pennsylvania exhibits that fertilizer usage in the agricultural phase and fuel combustion in the use phase are main contributors to biodiesel's life cycle environmental impacts for all blends. Comparing biodiesels with conventional diesel, environmental tradeoffs exist between global warming potential and eutrophication potential. Local scouring of biodiesels has the lowest environmental impacts for B20 and B100. Dietary shifts from dairy products and red meat to cereals can be an effective approach for lowering the personal nitrogen footprint. Altering farming practices (including shifting conventional tillage to no tillage, using manure, installing buffer strips surrounding farmlands etc) could reduce environmental impacts of bioproducts from life cycle perspectives too. The life cycle assessment analysis of bioproducts suggests environmentally benign farming practices and consumption shift to low nitrogen intensity foods to mitigate eutrophication issues.