Theoretical assessment of biomethane production from algal residues after biodiesel production

Abstract

Energy shortage, global warming, and climate changes call for the creation and breakthroughs of renewable and sustainable energy technologies, and thus biofuels from microalgae have been the object of ever-increasing interest. Microalgal biodiesel production presents as one of the promising options for biofuel production, since most microalgal species contain rich lipids. However, large amounts of residues are left behind after microalgal biodiesel production. In an effort to improve the potential economics of microalgal biofuels, it is essential to make full use of microalgal post-extracts. This Focus Article determines the theoretical yields of microalgal biodiesel and biomethane together with the relevant calorific values during the continuous production. Based on the investigated species, the microalgal biodiesel and biomethane yields widely range from 6 to 134 g/kg-VS and from 0.24 to 0.63 L/g-VS, respectively, while the total calorific values experience the range of between 6.88 and 18.80 MJ/kg-VS. Microalgal biodiesel production is not always required before anaerobic digestion, especially for those microalgal species with low lipid contents. Net energy ratio and cost-effectiveness analysis are highlighted in order to evaluate the viability of the biorefinery process. Wellfunded research and development programs can help develop technologies and policies, thus driving the industry toward prosperity.

A critical review on phycoremediation of pollutants from wastewater—a novel algae-based secondary treatment with the opportunities of production of value-added products

“…As per EC, (2016) biogas is expected to replace around 3.6% of fossil fuel that is used to produce electricity. As per Zhu et al,(Zhu, Li et al 2017), the energy stored in algae by virtue of photosynthesis can be converted into biogas, thus identifying a possible source of biogas production. According to the study of Pancha et al,(Pancha, Chokshi et al 2019) the C/N ratio plays a vital role in determining the biogas yielding ability of an algal strain, the higher the ratio, the better the yield.…”

Algae biogas production focusing on operating conditions and conversion mechanisms – A review

“…Biogas is a gas that is both combustible and caustic, being produced from any biomass of organic waste, including lignocellulose waste, grass, and leaves wastes, aquatic litter, microorganism waste, domestic solid refuse, and macro-algae. Usually, the composition of biogas is determined by the biomass used in the AD process as well as its operating conditions including, pH, temperature, pressure, and alkalinity, however, CH 4 , CO 2 , N 2 , H 2 , water, and traces of hydrogen sulfide (H 2 S) commonly found in biogas [ 9 , 10 ]. Biogas produced from algae wastes is attracting attention due to a high proportion of volatile solids providing large-scale production of renewable energy with a low carbon footprint and environmental impact while being economically viable [ 11 , 12 ].…”

Effects of Different Pretreatments on Improving Biogas Production of Macroalgae Fucus vesiculosus and Fucus serratus in Baltic Sea

“…15 The third-generation biofuels are made from micro-and macroalgae, which do not need much lands to cultivate and the marine biomass has relatively high yields compared to lignocellulosic feedstocks 16 and remove algae from the water body or the beach can diminish eutrophication of lakes, ponds, or oceans. 17 Brown algal families include Chordariaceae, Fucaceae, and Alariaceae. Fucus belongs to the Fucaceae algae.…”

“…The second-generation biofuels are made from rich lignocellulosic feedstocks, which need complicated pretreatments and expensive catalysts; such processes lead to high costs and these fuels have not much advantage on the market compared to fossil fuels . The third-generation biofuels are made from micro- and macroalgae, which do not need much lands to cultivate and the marine biomass has relatively high yields compared to lignocellulosic feedstocks and remove algae from the water body or the beach can diminish eutrophication of lakes, ponds, or oceans …”