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Life-Cycle Assessment and Uncertainty Analysis of Producing Biogas from Food Waste: A Case-Study of the First Dry-Process Biogas Plant in Sweden
Linköping University, Department of Management and Engineering, Environmental Technology and Management. Linköping University, Faculty of Science & Engineering. (Industrial Symbiosis)ORCID iD: 0000-0002-6736-6125
Linköping University, Department of Management and Engineering, Environmental Technology and Management. Linköping University, Faculty of Science & Engineering. (Industrial Symbiosis)
Linköping University, Department of Management and Engineering, Environmental Technology and Management. Linköping University, Faculty of Science & Engineering. (Industrial Symbiosis)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Anaerobic digestion of source-sorted food waste is increasing in Sweden. Traditionally, all large-scale co-digestion plants in Sweden, including the ones which digest food waste, are based on wet process. In this article life-cycle assessment (LCA) is used in order to investigate the environmental performance of the first dry-process biogas plant based on source-sorted municipal food waste in Sweden. The environmental performance of this plant is compared with existing typical plants which are based on wet process. Biogas production systems are complex, and there are knowledge gaps and large uncertainties regarding some of the processes. Most existing biogas LCA studies do not take into account these uncertainties and use single values in their life-cycle inventories. In this study uncertainty propagation in LCA of biogas production system is performed and the results are discussed in order to gain system-level insights on the main factors that influence the performance of producing biogas from food waste and the key uncertainties. An attributional process-based LCA model is used to study the global warming potential, eutrophication potential, acidification potential, and non-renewable cumulative energy demand of producing biogas from food waste. A reference case is used which is based on an actual biogas plant in Sweden which uses dry process for treating source-sorted food waste. For the wet process, this case is altered using Swedish literature data on wet digestion systems. For uncertainty management, a combination of approaches, including possibility/fuzzy intervals and stochastic distributions are used. Possibility/fuzzy intervals are used for data collection, but they are translated into probability distributions and Monte Carlo simulation. A simple method for quantifying the uncertainties of the LCA results is used, so the critical uncertainties can be assessed, compared, and discussed. In addition, several key performance indicators were introduced to complement the LCA results.The results of the LCA and KPIs show that using dry process for processing of food waste has a better or comparable environmental performance compared to most existing (wet-process) biogas plants in Sweden. When uncertainties are considered, two systems are more comparable. Regardless of the choice of wet or dry process for treatment of food waste, there are large uncertainties in the non-technical parts of the system which are less dependent to the technical choices or scenario assumptions. Decision-makers who are interested in using biogas systems for treatment of source sorted food waste, should take dry process into consideration. From an energy and environmental perspective, dry process can have good or better performance compared to many existing plants which are based on the wet process. This is mainly due to simpler pretreatment and digestate management. Taking into account the uncertainties (knowledge gaps, and variabilities) in assessing and comparing the performance of biogas production from food waste, provides a more realistic picture of their strengths and weaknesses. Since some of the impacts (and benefits such as carbon sequestration) of using food waste for biogas production and its digestate as biofertilizer lies in areas with high uncertainties, communication of these benefits to wider socio-political actors can play an important role for the development of biogas from food waste in Sweden, because many of the benefits of biogas solutions are not visible when analyzed by LCA approaches that do not take into account these uncertainties.

Keyword [en]
life-cycle assessment, key performance indicators, uncertainty analysis, food waste, biogas, dry process
National Category
Environmental Management
Identifiers
URN: urn:nbn:se:liu:diva-130774OAI: oai:DiVA.org:liu-130774DiVA: diva2:954663
Projects
BRC-RP3 (system quantification projects)-Biogas from Food waste
Funder
Swedish Energy AgencyLinköpings universitet
Available from: 2016-08-23 Created: 2016-08-23 Last updated: 2016-08-23Bibliographically approved
In thesis
1. Systems Analysis for Eco-Industrial Development: Applied on Cement and Biogas Production Systems
Open this publication in new window or tab >>Systems Analysis for Eco-Industrial Development: Applied on Cement and Biogas Production Systems
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Systemanalys för ekoindustriell utveckling : tillämpadpå cement och biogas produktion
Abstract [en]

Our industrial systems are not sustainable—a major challenge which demands several types of responses. Eco-industrial development can be seen as such a response, with the goal to establish industrial systems that are both ecological and economical. Industrial Ecology is another closely related response. It is based on the idea that natural systems can be used to understand how to design sustainable industrial systems, for example, by shifting from linear industrial processes to cyclic systems, where waste streams can be avoided or minimized through utilization as raw materials for other processes. In this thesis, the possible contributions of industrial ecology/symbiosis to eco-industrial development are investigated through the use of systems analysis approaches. Two systems analysis methods are used: life-cycle assessment and multi-criteria analysis. These methods are applied on two types of industrial systems: cement and biogas.

Cement is among the most used materials in the world with extensive resource consumption and environmental impact, manifested for example by the high levels of CO2 emissions. Multi-criteria analysis was used to identify, classify, and assess different measures to improve the climate performance of cement production, while life-cycle assessment was employed to quantify the CO2 emissions. Combined, multi-criteria analysis and life-cycle assessment were used for an integrated assessment of different eco-industrial development paths. Most of the feasible and resource-efficient improvement measures were related to utilization of secondary resources, for example minimizing the clinker content of the cement by replacing it with by-products from steel and iron manufacturing, or using refuse-derived fuels. Effective utilization of these secondary raw materials and fuels can be achieved through industrial symbiosis.

Biogas is viewed as part of a larger transition towards a bio-based economy where resources—bio-materials and bio-energy—are used in a cascading, circular, and renewable manner. Multi-criteria analysis was used to assess the feasibility and resource efficiency of using different types of biomass as feedstock for biogas and biofertilizer production. In addition to aspects such as renewable energy and nutrient recycling, cost efficiency, institutional conditions, environmental performance, the potential per unit, and the overall potential were considered. In another study, life-cycle assessment was used to analyze the environmental performance of biogas production from source-sorted food waste using a dry digestion process. The study showed that the performance of this dry process is superior to most of the existing wet biogas processes in Sweden. The critical sources of uncertainty and their impact on the overall performance of the system were analyzed. Factors influencing methane production, as well as processes related to soil after the digestate is applied as biofertilizer on land, have the greatest influence on the performance of these systems.

For both cement and biogas systems industrial symbiosis involving collaboration and better utilization of local/regional secondary resources, can result in resource-efficient eco-industrial development. Life-cycle assessment and multi-criteria approaches can serve as two complementary methods for investigating the feasibility, potential, and resource efficiency of different development paths. These approaches can provide input into decision-making processes and lead to more informed decisions.

Abstract [sv]

Våra industriella system är inte hållbara—en stor utmaning som kräver olika typer av åtgärder. Ekoindustriell utveckling kan betraktas som en sådan åtgärd, eller respons, med avsikten att etablera industriella system som både är sunda ekonomiskt och ekologiskt. Industriell ekologi är en annan och närbesläktad respons, baserad på idén att naturliga system kan användas som förebilder, för att förstå hur hållbara industriella system kan designas. Det kan tillexempel handla om ett skifte från linjära industriella processer till cykliska, där avfallsströmmar kan undvikas eller minimeras genom att de omvandlas till råvaror för andra processer. I den här avhandlingen undersöks om och hur industriell ekologi/symbios kan bidra till fortsatt ekoindustriell utveckling, genom användning av systemanalysmetoder. Två typer av industriella system står i fokus: cement- och biogasproduktion. Vidare används två typer av miljösystemanalytiska metoder: livscykelanalys och multikriterieanalys.

Cement är ett av världens mest använda material och är förknippat med omfattande resursanvändning och stor miljöpåverkan, exempelvis i form av höga utsläpp av koldioxid. Multikriterieanalys användes för att identifiera, klassificera och bedöma ett flertal förbättringsåtgärder som kan ge bättre klimatprestanda. Livscykelanalys användes för att kvantifiera utsläppen av koldioxid. Kombinerade användes multikriterieanalys och livscykelanalys för en form av integrerad bedömning av olika ekoindustriella utvecklingsvägar för cementindustrin. De flesta förbättringsåtgärderna som bedömdes vara genförbara och resurseffektiva var kopplade till användning av sekundära resurser, exempelvis i form av att mängden cementklinker minimerades och ersattes av restprodukter från järn- och stålindustrin samt att  avfall användes som bränsle. Effektiv användning av den här typen av sekundära material kan realiseras genom industriell symbios.

Biogas ses som en del i en större omställning i riktning mot en biobaserad ekonomi, där biomaterial och bioenergi används i kaskadsystem —förnyelsebart och cirkulärt. Multikriterieanalys tillämpades för att utvärdera genomförbarhet och resurseffektivitet för olika substrat till biogas- och biogödselproduktion. Aspekter avseende förnyelsebar energi och näringscirkulering beaktades, även kostnadseffektivitet, sociala och institutionella förutsättningar, miljöprestanda, potentialen per enhet samt potentialen totalt. I en annan studie användes livscykelanalys för att studera miljöprestandan för biogasproduktion baserad på utsorterat matavfall i en torr rötningsprocess. Studien visade att den torra processen hade bättre eller likvärdig prestanda jämfört med många av de våta processer som används för motsvarande ändamål i Sverige. Kritiska källor till osäkerheter och deraspåverkan på den totala prestandan för systemet analyserades. Störst betydelse hade de faktorer som påverkar metanproduktionen samt processer i jorden/marken efter att digestatet lagts ut som biogödsel.

Både för cement och biogassystem kan industriell symbios, som involverar samverkan mellan lokala/regionala aktörer och användning av sekundära resurser, leda till resurseffektiv ekoindustriell utveckling. Livscykelanalys och multikriterieanalys kan användas som två kompletterade metodologiska approacher för att undersöka genomförbarhet, potential och resurseffektivitet för olika utvecklingsvägar. Dessa metoder kan bidra till beslutsfattandet och stödja mer välgrundade beslut.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2016. 125 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1780
Keyword
industrial ecology, eco-industrial development, multi-criteria analysis, life-cycle assessment, MCA, LCA, uncertainty management, systems analysis, industrial symbiosis, cement, biogas, cement production, biogas solutions
National Category
Environmental Management
Identifiers
urn:nbn:se:liu:diva-130782 (URN)9789176857083 (Print) (ISBN)
Public defence
2016-09-09, ACAS, A-Building, Campus Valla, Linköping University, Linköping, 14:22 (English)
Opponent
Supervisors
Funder
Swedish Energy Agency
Available from: 2016-08-23 Created: 2016-08-23 Last updated: 2016-08-23Bibliographically approved

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