Biorefineries using waste – production of energy and chemicals from biomasses by micro-organisms - Biomass as Energy Source: Resources, Systems and Applications - page 236

Common substrates in agricultural biogas plants are (Thorin et al. , 2011):
• liquid and solid wastes from livestock husbandries (like manure),
• ensiled energy crops,
• harvesting residues,
• residues from waste material market.
The most important chemical and material from the biorefineries products are the following
(Cherubini, 2010):
•

chemicals (fine chemicals, building blocks, bulk chemicals),

•

organic acids (succinic, lactic, itaconic and other sugar derivatives),

• polymers and resins (starch-based plastics, phenol resins, furan resins),

• biomaterials (wood panels, pulp, paper, cellulose),

• food and animal feed,

• fertilizers.

This list is illustrating the fact that bio-industries powered by microbes could be replacing the
petrochemical industries gradually.
In anaerobic digestion biogas, mainly consisting of methane, is produced. A large variety of
wastes are digested such as sludge fromwaste water treatment plants, grease trap sludge, manure,
bio-waste, municipal solid waste, food wastes, refuse derived fuel and industrial waste water.
Another biological conversion process that can use waste as feedstock is fermentation to ethanol
or butanol. Wastes of interest for fermentation are industrial wastewaters and lignocellulosic
wastes such as straw and wood wastes. Fermentation of sugary wastes to ethanol is a mature and
well-proven technology but fermentation of lignocellulosic waste and fermentation to butanol is
still at the research stage (Thorin et al. , 2011). One lucrative possibility could be the combination
of different wastes, or new materials, as starting point for industrial processes.
The exploitation of fats derived from animal and plant kingdoms is an industrially feasible
approach (Metzger and Bornscheuer, 2006). Due to their pure aliphatic structure, the fatty acids
can be readily combusted as fuel. They are also potential raw materials for various chemicals
(Metzger and Bornscheuer, 2006).
Proteins are abundant in food and are vital to nutrition and biochemical function (Barone and
Schmidt, 2006). They are derived from agricultural sources and used in everyday products such
as glues and textiles. They are also used as replacements for several petroleum-derived materials.
Proteins are the source of polymers for fiber, molded plastics, films, and an array of products.
They constitute a sustainable resource and can often be processed in the same way as conventional
synthetic polymers.

13.4 MICROBES CARRY OUT THE REACTIONS WITH ENERGETICALLY
FEASIBLE BIOCATALYSIS

Traditional biotechnology could be determined by some ideals into technologies where bio-
catalysis is applied for the process management. Therefore, such applications as e.g. biodiesel
production fall outside this concept. On the other hand, if biocatalysis is involved, it usually is
also a sign of energetically feasible manufacturing system.

13.4.1 Ecological thinking based on understanding microscopic interactions
Microbial interactions are differing from the ones of zoological ecology, where various individual
encounter occasionally. The microbes are continuously living in a “biochemical universe.” They
are under the influences of the surrounding chemical gradients. If active, they have to deal,
besides with the physicochemical circumstances, also with their own metabolic products. In the
microscopic world, they are also subjected to the signaling of other cells and populations.