Assessing the Environmental Performance of Integrated Ethanol and Biogas Production

Abstract

As the production of biofuels continues to expand worldwide, criticism about, e.g. the energy output versus input and the competition with food has been questioned. However, biofuels may be optimized to increase the environmental performance through the concepts of industrial symbiosis. This paper offers a quantification of the environmental performance of industrial symbiosis in the biofuel industry through integration of biogas and ethanol processes using a life cycle approach. Results show that although increasing integration is assumed to produce environmental benefits in industrial symbiosis, not all impact categories have achieved this and the results depend upon the allocation methods chosen.

Degree of Biomass Conversion in the Integrated Production of Bioethanol and Biogas

“…The differences in the amount of biogas volume obtained, on the other hand, are mainly related to the quality of the alcoholic fermentation process, which directly affects the content of organic matter (in the stillage), which is a nutrient substance for anaerobic digestion bacteria [63]. It serves as the confirmation that these processes function in an integrated manner and remain in industrial symbiosis with each other [64,65] to comprehensively utilise organic matter for energy purposes. A full understanding of the mechanism of this concept provides an opportunity to undertake process optimisation in accordance with the technological principle of using the raw material and the energy stored in it most effectively.…”

“…In addition to the previously discussed use of ethanol byproducts for biogas production, other applications include the use of glycerol from biodiesel production for biogas production, the use of digestate from biogas plants as a fertilizer, and the use of sewage treatment byproduct (sewage sludge) as a substrate in biogas plants (preferably adjacent to sewage treatment plants) [21,24,36]. Publications related to the topic of the integrated production of bioethanol and biogas mainly address: (i) local and global symbiotic activities (potential acidification and eutrophication due to system expansion, and global benefits); (ii) maize pretreatment methods (improving access to cellulose in maize silage and extracting hemicellulose sugars from maize silage fibres by, e.g., steam pretreatment, with or without a catalyst) that increase the efficiency of ethanol production [66,67]; and (iii) applications of new, interesting raw biomaterials for bioethanol and biogas production-such as a species of wild inedible cassava, Manihot glaziovii (tubers obtained from three different areas in Tanzania) [68]-a general evaluation of the efficiency of the process [65,69], and its economic aspects [70]. As previously mentioned, the efficiency scores of the bioethanol production process, including methane, quoted from other papers are comparable to those presented in this study.…”

Nonrenewable Energy Cost and Greenhouse Gas Emissions of a “Pig-Biogas-Fish” System in China

“…Some focused on the biogas technologies designed in laboratory [ 13 , 14 ], and some focused on the biogas engineering itself [ 15 , 16 ]. Patterson et al [ 17 ] provided an assessment of biogas systems on a regional scale in the UK that can provide guidance on infrastructure development decisions; Martin et al [ 18 ] utilized a life cycle approach to present the environmental impacts of the integration of biogas and ethanol processes; Wei et al [ 19 ] assessed the efficiency and sustainability of the “Four in One” ecological economic system for peach production system in Beijing by life cycle energy analysis; Wang et al [ 20 ] calculated and evaluated the energy conservation and the emission reductions of the rural household biogas project in China by establishing the LCA method. In these previous researches, when setting the system boundary, human factors play a significant role.…”