Biochemical production of bioenergy from agricultural crops and residue in Iran

Abstract

The present study assessed the potential for biochemical conversion of energy stored in agricultural waste and residue in Iran. The current status of agricultural residue as a source of bioenergy globally and in Iran was investigated. The total number of publications in this field from 2000 to 2014 was about 4294. Iran ranked 21st with approximately 54 published studies. A total of 87 projects have been devised globally to produce second-generation biofuel through biochemical pathways. There are currently no second-generation biorefineries in Iran and agricultural residue has no significant application. The present study determined the amount and types of sustainable agricultural residue and oil-rich crops and their provincial distribution. Wheat, barley, rice, corn, potatoes, alfalfa, sugarcane, sugar beets, apples, grapes, dates, cotton, soybeans, rapeseed, sesame seeds, olives, sunflowers, safflowers, almonds, walnuts and hazelnuts have the greatest potential as agronomic and horticultural crops to produce bioenergy in Iran. A total of 11.33million tonnes (Mt) of agricultural biomass could be collected for production of bioethanol (3.84gigaliters (Gl)), biobutanol (1.07Gl), biogas (3.15billion cubic meters (BCM)), and biohydrogen (0.90BCM). Additionally, about 0.35Gl of biodiesel could be obtained using only 35% of total Iranian oilseed. The potential production capacity of conventional biofuel blends in Iran, environmental and socio-economic impacts including well-to-wheel greenhouse gas (GHG) emissions, and the social cost of carbon dioxide reduction are discussed. The cost of emissions could decrease up to 55.83% by utilizing E85 instead of gasoline. The possible application of gaseous biofuel in Iran to produce valuable chemicals and provide required energy for crop cultivation is also studied. The energy recovered from biogas produced by wheat residue could provide energy input for 115.62 and 393.12 thousand hectares of irrigated and rain-fed wheat cultivation in Iran, respectively. The nitrogen requirement for 33.6% of the total wheat cultivation area could be supplied by the ammonia acquired from biohydrogen. A discussion of the logistics of collection and transportation of the biomass and sensitivity analysis are carried out to evaluate the effect of field cover factor, crop yield, and well-to-wheel GHG emission on collectable residue, biofuel production, and GHG emissions.

Keywords: Agricultural residues; Bioenergy; Biofuels; Greenhouse gas emissions; Iran; Social cost of carbon.