Environmental impacts of producing bioethanol and biobased lactic acid from standalone and integrated biorefineries using a consequential and an attributional life cycle assessment approach

Ranjan Parajuli; Marie Trydeman Knudsen; Morten Birkved; Sylvestre Njakou Djomo; Andrea Corona; Tommy Dalgaard

doi:10.1016/j.scitotenv.2017.04.087

Environmental impacts of producing bioethanol and biobased lactic acid from standalone and integrated biorefineries using a consequential and an attributional life cycle assessment approach

Sci Total Environ. 2017 Nov 15:598:497-512. doi: 10.1016/j.scitotenv.2017.04.087. Epub 2017 Apr 25.

Authors

Ranjan Parajuli¹, Marie Trydeman Knudsen², Morten Birkved³, Sylvestre Njakou Djomo², Andrea Corona³, Tommy Dalgaard²

Affiliations

¹ Department of Agroecology, Aarhus University, Blichers Allé 20, DK-8830 Tjele, Denmark. Electronic address: ranjan.parajuli@agro.au.dk.
² Department of Agroecology, Aarhus University, Blichers Allé 20, DK-8830 Tjele, Denmark.
³ Department of Management Engineering, Technical University of Denmark, Building 424, DK-2800 Lyngby, Denmark.

PMID: 28448939
DOI: 10.1016/j.scitotenv.2017.04.087

Abstract

This study evaluates the environmental impacts of biorefinery products using consequential (CLCA) and attributional (ALCA) life cycle assessment (LCA) approaches. Within ALCA, economic allocation method was used to distribute impacts among the main products and the coproducts, whereas within the CLCA system expansion was adopted to avoid allocation. The study seeks to answer the questions (i) what is the environmental impacts of process integration?, and (ii) do CLCA and ALCA lead to different conclusions when applied to biorefinery?. Three biorefinery systems were evaluated and compared: a standalone system producing bioethanol from winter wheat-straw (system A), a standalone system producing biobased lactic acid from alfalfa (system B), and an integrated biorefinery system (system C) combining the two standalone systems and producing both bioethanol and lactic acid. The synergy of the integration was the exchange of useful energy necessary for biomass processing in the two standalone systems. The systems were compared against a common reference flow: "1MJ_EtOH+1kg_LA", which was set on the basis of products delivered by the system C. Function of the reference flow was to provide service of both fuel (bioethanol) at 99.9% concentration (wt. basis) and biochemical (biobased lactic acid) in food industries at 90% purity; both products delivered at biorefinery gate. The environmental impacts of interest were global warming potential (GWP₁₀₀), eutrophication potential (EP), non-renewable energy (NRE) use and the agricultural land occupation (ALO). Regardless of the LCA approach adopted, system C performed better in most of the impact categories than both standalone systems. The process wise contribution to the obtained environmental impacts also showed similar impact pattern in both approaches. The study also highlighted that the recirculation of intermediate materials, e.g. C₅ sugar to boost bioethanol yield and that the use of residual streams in the energy conversion were beneficial for optimizing the system performance.

Keywords: Attributional LCA; Biobased products; Biorefinery; Consequential LCA; Economic allocation; Indirect land use change; System expansion.