Experimental evaluation and optimization of the anaerobic digestibility of two new desert weeds for biogas production

Today, the energy crisis, increasing emissions, and global warming have been crucial challenges in the world, especially in developing countries, and the use of renewable energies can be a good solution for these problems. Biogas is a renewable energy that has numerous benefits, including the production of fertilizers, increasing public health, control of diseases, and especially the production of clean energy. Therefore, methane production from weeds can be an attractive method to supply renewable fuel. The present study aimed to evaluate the potential of producing biogas from two new desert weeds, Sophora alopecuroides and Alhagi maurorum, on a lab-scale in four 2.4 L digestion tanks at room temperature (33 ± 2 °C) in two stages. Also, the effects of various parameters such as pH and different biomass:water ratios on methane production have been investigated. The produced gas compositions were analyzed using gas chromatography-thermal conductivity detector (GC-TCD). The quantities of biogas produced from both plants were determined at different biomass to water ratios and finally, the optimal ratio for each plant was determined. The quantity of optimal cumulative biogas production in 10 days was 2324 and 3099 ml for A. maurorum (biomass:water ratio = 1:5) and S. alopecuroides (biomass:water ratio = 1:6), respectively. The results proved that S. alopecuroides produced 33.34% more biogas compared to A. maurorum. The presence of high volatile solids and low dry solids, and higher carbon:nitrogen ratio (three times) in A. maurorum compared to S. alopecuroides are the effective factors in the production of the lower amount of biogas in this plant.