A GIS based approach to investigating the potential of herbaceous bioenergy feedstocks for cellulosic bioethanol production in Nigeria

Abstract

Cellulosic ethanol provides a global alternative transport fuel to substitute conventional fossil fuels. The Nigerian Biofuel Policy in 2005 mandated the production and blending of gasoline with 10% bioethanol. Although, there have been indications that Nigeria has sufficient land available for 1st generation biofuel production, there is an urgent need to achieve food security for an increasing population. To these effects, this study aimed to investigate the land requirement and production potential of purposely grown herbaceous energy crops for 2nd generation cellulosic ethanol production in the six geo-political zones and states of Nigeria to meet the government Biofuel Policy. In this study, ArcGIS software was first used to identify two target land use classes (grassland and shrubland) with the potential for cellulosic ethanol production. The two land use classes were evaluated both on a regional and state basis. The study further employed a GIS-based multi-criteria decision method to determine land suitability for four herbaceous bioenergy crop species (Alfalfa, Elephant grass, Miscanthus x giganteus and Switchgrass). Suitability analysis was conducted using literature-based criteria weights for temperature, rainfall, soil organic matter, soil pH, slope and elevation by zone and state. The study further integrated Python software with ArcGIS to evaluate biomass productivity of the 4 species, where the NE zone was found to record the overall highest potential across the country, the SW was the highest in the South while SE zone generally possessed the least potential for all species. Estimates of productivity by state showed that Borno is the most potential productive state in the North and Oyo in the South. Lagos, which is largely comprised of built up areas, is the state with the least potential. In terms of crop productivity, elephant grass showed highest production potential followed by Miscanthus x giganteus and switchgrass while the C3 species (Alfalfa) has the least potential. The theoretical ethanol yield based on cellulose content of each bioenergy crop showed that at a national level, elephant grass has the greatest potential of the four species at 338 billion litres production per annum, which can power 735 large-scale cellulosic ethanol processing facilities. Generally, the study demonstrated that Nigeria will require the construction of multiple process facilities in order to be able to sustainably use the potential feedstocks available. Furthermore, the study showed that Nigeria has the potential to produce about 66 billion litres of cellulosic bioethanol per annum from the range of feedstocks evaluated. It is to this effect that the study indicated that Nigeria could potentially exceed the proposed 10% biofuel target of about 2 billion litres per annum using purposely grown herbaceous energy crops for cellulosic ethanol production.