Methodological considerations, drivers and trends in the life cycle analysis of bioproducts

It is important to assess the relative environmental performance of bioproducts compared to their conventional (fossil-based) counterparts and to identify additional opportunities to improve bioproducts' environmental impacts. This chapter examines the application of life cycle analysis (LCA) to these purposes and includes a discussion of LCA methodology including treatment of bioproduct feedstocks, conversion process analysis, and end-of-life assumptions. Decisions an LCA practitioner makes about bioproduct end-of-life are especially influential in calculations of bioproduct life-cycle greenhouse gas (GHG) emissions. Options for end-of-life treatment including complete or partial degradation in a landfill and combustion with and without energy recovery are discussed using polyethylene as an example. Another critical issue in bioproduct LCA that this chapter discusses is treatment of co-products. Moreover, we present life-cycle GHG emissions and fossil energy consumption (FEC) for eight bioproducts (propylene glycol, 1,3-propanediol, 3-hydroxypropionic acid, acrylic acid, polyethylene, isobutanol, succinic acid, and 1,4-butanediol) produced from either corn stover or algae. With the exception of 3-hydroxypropionic acid, which has no fossil-derived counterpart, all of the bioproducts included in this study exhibited lower life-cycle GHG emissions and FEC than the same compound produced from fossil sources. In addition to GHG and energy consumption metrics, life-cycle water consumption is also key because of concerns about water consumption used to grow biomass. This chapter presents estimates of the water intensity of the feedstock production stage of each of the considered bioproducts. These estimates are dependent upon the location of feedstock growth and, in the case of algae, assumptions about the portion of water that comes from municipal waste water treatment plant effluent.