Biomass is a promising renewable energy source and its significance is escalating in the context of climate change and depletion of fossil foils. This study was conducted for two consecutive years 2016 and 2017, using five sorghum cultivars, i.e., JS-263, Jawar-2011, Hagari, JS-2002, and YS-2016, in order to determine the best cultivars in terms of dry matter yield, chemical composition, and biomethane yield grown under semi-arid conditions in Pakistan. The results revealed that sorghum cultivars responded differently in terms of growth, biomass yield, chemical composition, and methane yield. Cultivars Jawar-2011 produced maximum leaf area index, leaf area duration, crop growth rate, plant height, and leaves per plant, however, they were comparable with Sorghum-2016, whereas cultivar JS-2002 performed poorly among the tested cultivars. Similarly, cultivar Jawar-2011 produced maximum dry matter yield (16.37 t ha-1) similar to that of YS-2016, further cultivar JS-2002 performed poorly and gave lower dry matter yield (12.87 t ha-1). The maximum protein concentration (10.95), neutral detergent fibers (61.20), and lignin contents (5.55) found in Jawar-2011 were comparable with those in YS-2016, while the lowest neutral detergent fiber and lignin contents were found in JS-2002. Although JS-2002 produced the highest specific methane yield per kilogram of volatile solids, it was overcompensated by Jawar-2011 owing to higher dry matter yield per hectare. These results suggested that cultivar Jawar-2011 can be grown successfully in semi-arid conditions of Pakistan in order to get good biomass yield along with higher methane yield.
Keywords: Biomass quality; Biomethane yield; Crop growth rate; Cultivars; Leaf area duration.