Bioconversion Process of Barley Crop Residues into Biogas—Energetic-Environmental Potential in Spain

Abstract

Barley fields reach 1.7 million hectares in Spain, of which 320,000 are used to produce malt, generating 450,000 tons of crop residue from barley intended for malt production. One way to treat this waste in an environmentally sound, energy-sustainable and economically cost-effective manner is anaerobic digestion. The biogas generated can be used as fuel and as a renewable source of energy (providing a solution to the energy supply problem from an environmental point of view). It has been shown that, when treated along with sludge from a Upflow Anaerobic Sludge Blanket (UASB) reactor, the crop malt residue produces about 1604 NmL of biogas per 100 g; with a content in methane of 27.486%. The development of the process has been studied with a novel indicator, hydrogen generation, and it has been determined that the process takes place in two phases. It has been demonstrated that this solution is beginning to be energy-efficient and therefore to produce energy for external uses in regions that have at least 6000 hectares of planted barley. At best, it can be considered, in a given region, the equivalent of a 115 MW power plant. It could supply energy to 10 thousand homes per year. Therefore, it is considered an energy-efficient solution that com-plies with the Sustainable Development Goals #1, #7, #10, #12 and #13. It guarantees access to energy in isolated areas or with supply problems, and results in a 55.4% reduction in emissions of equivalent-CO2 (which equals 38,060 tons of equivalent-CO2 in Spain).

Pretreatment of Crop Residues for Bioconversion

“…The models were successfully verified for wheat bran hydrolysate, which was found to be an outstanding substrate for xylitol production by C. boidinii, while the use of rice straw hydrolysate requires further research. In another article on bioconversion, Morales-Polo et al report the anaerobic digestion of barley (Hordeum vulgare L.) crop residues for energy uses [24]. Substrate characterization and analysis of the anaerobic digestion process through all phases are discussed, and the potential for biogas and methane generation is determined.…”

Current state of biogas and biomethane production and its implications for Spain

“…Spain has great potential to produce biogas and biomethane, mainly from biomass resources (livestock, food waste and agricultural waste). 17 However, the regulations are very relaxed to encourage electricity generation projects due to the significant decrease in the feed-in tariff systems and the abolishment of financial support mechanisms, which resulted in a significant slowdown in the development of renewables after 2015. 18 In addition, although Spain currently has a gas infrastructure of more than 100 000 kilometers of distribution network already prepared for the circulation of biomethane, only 6 facilities currently produce biomethane and inject it into the network, and thus greater effort is needed for implementation installations in the coming years.…”

Calorific Value of Festuca rubra Biomass in the Phytostabilization of Soil Contaminated with Nickel, Cobalt and Cadmium Which Disrupt the Microbiological and Biochemical Properties of Soil

“…Therefore, specialist logistic operations and processing treatments are required to optimize these parameters [25]. Different types of biomass also require specific conversion processes [26][27][28][29][30].…”