Attributional life cycle assessment (ALCA) of polyitaconic acid production from northeast US softwood biomass

Abstract

Shifting the resource base for chemical and energy production from fossil feed stocks to renewable raw materials is seen by many as one of the key strategies towards sustainable development. The objective of this study is to assess the environmental burdens of producing polyitaconic acid (PIA), a water-soluble polymer derived from itaconic acid identified by the US Department of Energy as one of the top 12 value added chemicals from northeast (NE) US softwood biomass. Results are compared to corn-derived PIA and fossil-based poly acrylic acid (PAA) on the basis of 1 kg of polymer at the factory gate. This study uses attributional life cycle assessment to quantify global warming potential (GWP), fossil energy demand (CED), acidification, eutrophication, water use, and land occupation of the polymer production routes. This includes feedstock growth and harvest, sugar extraction, fermentation, itaconic acid recovery, and subsequent polymerization. Foreground data for softwood-derived PIA comes from lab- and pilot plant runs undertaken by Itaconix LLC. Results indicate that the use of softwood-based PIA may be advantageous in terms of GWP, CED, and acidification when compared to both, the integrated corn biorefinery and fossil-based PAA production. When looking at impacts to eutrophication and water use, the use of softwood leads to lower potential impacts compared to its corn-based counterpart but to higher impacts when compared to fossil-based PAA. Land occupation, to a large extent, due to lower yields and longer growth cycles associated with softwood growth in the NE, is highest for softwood-derived PIA and lowest for fossil-based PAA. Environmental impacts are mainly the results of onsite electricity use, inputs of activated carbon and sodium hydroxide, as well as water use during sugar extraction and fermentation. Assumptions with regards to allocation, activated carbon inputs, and electricity mixes to processes of the foreground system are tested in a sensitivity analysis. Wood-derived PIA production may be an interesting alternative to current fossil-based pathways and could contribute to a future biobased economy. However, currently, land occupation, water use, and eutrophication are high when compared to traditional PAA production. The use of short rotation crops or waste feedstocks and optimization with regards to water requirements and reuse should be investigated to further lower system-wide impacts.