ABSTRACT
This review showcases a comprehensive analysis of studies that highlight the different conversion procedures attempted across the globe. The resources of biogas production along with treatment methods are presented. The effect of different governing parameters like feedstock types, pretreatment approaches, process development, and yield to enhance the biogas productivity is highlighted. Biogas applications, for example, in heating, electricity production, and transportation with their global share based on national and international statistics are emphasized. Reviewing the world research progress in the past 10 years shows an increase of ~ 90% in biogas industry (120 GW in 2019 compared to 65 GW in 2010). Europe (e.g., in 2017) contributed to over 70% of the world biogas generation representing 64 TWh. Finally, different regulations that manage the biogas market are presented. Management of biogas market includes the processes of exploration, production, treatment, and environmental impact assessment, till the marketing and safe disposal of wastes associated with biogas handling. A brief overview of some safety rules and proposed policy based on the world regulations is provided. The effect of these regulations and policies on marketing and promoting biogas is highlighted for different countries. The results from such studies show that Europe has the highest promotion rate, while nowadays in China and India the consumption rate is maximum as a result of applying up-to-date policies and procedures.
ABSTRACT
The Impact Assessment (IA) step in Life Cycle Assessment (LCA) studies is classified into three steps of characterization, normalization and weighting. In this research, various impact categories were weighted using Analytic Hierarchy Process (AHP), as a multi criteria decision making tool. Iranian tobacco production system was the example of agricultural system. The data for LCA analysis were collected from 225 farms. The data for AHP analysis were gathered by surveying 12 LCA experts. The results indicated that on-farm emissions of CO2, CH4, N2O, NH3, NOx and SO2 were accounted for 25, 96, 93, 99, 21 and 2% of the total emissions (cradle to farm gate), respectively. The characterization indices for the impact categories of acidification, terrestrial eutrophication, global warming, phosphate resources depletion, potash resources depletion and fossil resources depletion for one ton tobacco production were calculated to be 13.87 kgSO2eq, 19.69 kgNOxeq, 1883.90 kgCO2eq, 19.69 kgNOxeq, 4.19 kgP2O5, 6.14 kgK2O, and 59,659.23 MJ, respectively. The LCAâ¯+â¯AHP showed that the weighted factors of global warming, terrestrial eutrophication, acidification, fossil resources depletion, phosphate resources depletion and potash resources depletion were 1, 0.790, 0.518, 0.681, 0.422, and 0.263, respectively. Many agricultural systems could benefit from using the developed weighting factors for LCA studies in the agricultural sector. Based on the new developed weighted factors, the weighted indices of aforementioned impact categories for Iranian tobacco production were 0.24, 0.41, 0.19, 1.04, 0.23, and 0.20, respectively. This implies that fossil resources depletion impact category was attributed the highest negative environmental impacts of tobacco production followed by terrestrial eutrophication.
