Opportunities for renewable bioenergy using microorganisms

Abstract

Global warming can be slowed, and perhaps reversed, only when society replaces fossil fuels with renewable, carbon-neutral alternatives. The best option is bioenergy: the sun's energy is captured in biomass and converted to energy forms useful to modern society. To make a dent in global warming, bioenergy must be generated at a very high rate, since the world today uses $10 TW of fossil-fuel energy. And, it must do so without inflicting serious damage on the environment or disrupting our food supply. While most bioenergy options fail on both counts, several microorganism-based options have the potential to produce large amounts of renewable energy without disruptions. In one approach, microbial communities convert the energy value of various biomass residuals to socially useful energy. Biomass residuals come from agricultural, animal, and a variety of industrial operations, as well as from human wastes. Microorganisms can convert almost all of the energy in these wastes to methane, hydrogen, and electricity. In a second approach, photosynthetic microorganisms convert sunlight into biodiesel. Certain algae (eukaryotes) or cyanobacteria (prokaryotes) have high lipid contents. Under proper conditions, these photosynthetic microorganisms can produce lipids for biodiesel with yields per unit area 100 times or more than possible with any plant system. In addition, the non-lipid biomass can be converted to methane, hydrogen, or electricity. Photosynthetic microorganisms do not require arable land, an advantage because our arable land must be used to produce food. Algae or cyanobacteria may be the best option to produce bioenergy at rates high enough to replace a substantial fraction of our society's use of fossil fuels.

Biomethane production from starch and lignocellulosic crops: a comparative review

“…9 Because of this, approaches relying on the use of food crops for biofuel production are failing to meet renewable criteria since they compete with food production for high-grade arable land and their bioenergy output is limited. 10 In ef ect, the food versus fuel debate is making it hard to justify the diversion of lands traditionally harvested for human feed and convert them into lands harvested for transportation. h ese i rst-generation biorei neries, operating from i rst-generation crops, were probably a necessary step in the evolution toward more sustainable practices for renewable energy production.…”

Renewable sustainable biocatalyzed electricity production in a photosynthetic algal microbial fuel cell (PAMFC)

“…In the present study, we focus on living microalgae for solar energy capturing and bacteria in the MFC for electricity generation. These concepts of living green biomass and MFCs are attractive, since they can, in potential, generate energy in a renewable, sustainable, and efficient manner (Rittmann 2008;Strik et al 2008a, b;Ter Heijne et al 2006).…”

Screening and evaluation of non-heterocystous filamentous cyanobacteria for lipid and commercially viable fatty acids

“…Lipids (accumulated in the thylakoid membranes) are associated with high levels of photosynthesis and rapid growth rate and are of particular interest, since they can be used for biodiesel production [7][8]. Microalgae accumulate large amounts of lipids as reserve material, with especially in conditions of stress and slow growth [9]. The fatty acid composition of marine microalgae has been studied more extensively [10]; [11]; [12]; [13] than the freshwater forms [14]; [15]; [16].…”