Figure1: acetogenic bacteria is said to convert










Figure1: Anaerobic Pathway, 7


Previous reports show that hydrolytic and
fermentative bacteria is thought to have been responsible for the initial
attack on polymers and monomers found in biomass for the hydrolysis stage of
anaerobic digestion. In this case they are said to produce mainly acetate and
hydrogen, with some varying amounts of volatile fatty acids (VFA) such as
propionate and butyrate as well as some alcohols. The sole purpose for this
process is to produce acetate and hydrogen. In which case, the obligate
hydrogen-producing acetogenic bacteria is said to convert propionates and
butyrate into hydrogen and acetate.  Two
groups of methanogenic archaea are then said to produce methane from either
acetate or hydrogen respectively.

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Fats, oils,

Acids &

Long chain
fatty acids

Acetic acid



Propionic, Butyric, Lactic



• Methanogenesis


• Fermentation



There exist several processes leading to
methane production from biomass which could vary from “relatively
humid-biomass-based, low temperature-and hence slow processes” generally called
biochemical processes in distinction from processes which could be described as
“relatively dry- biomass-based, high temperature and hence fast processes”
generally called thermochemical process. The anaerobic digestion process is one
of the biochemical processes during which the organic matter (decomposed form
of organic material or biomass) is broken down by a consortium of
microorganisms within a liquid medium in the absence of oxygen leading to the
formation of digestate (liquid phase-by-product) and biogas which mainly
consist of methane and carbon dioxide in addition to some trace elements like
Hydrogen Sulphide and Water depending on feedstock used. This digestate which
is the decomposed substrate resulting from biogas production can be used as a
bio-fertilizer 3. The pathway anaerobic
digestion is displayed in Figure 1.1. In this pathway, anaerobic digestion was
initially perceived as a two-stage process involving the sequential action of
acid forming and methane forming bacteria. In the present context, it is known
to be a complex fermentation process brought about by the symbiotic association
of different types of bacteria 4,5,6 where
by, the products produced by one group of bacteria serve as the substrates for the
next group. The main sequences involved in this new model can be classi?ed into
four principal groups composing of:

Anaerobic Digestion Process


 In recent
years, research and technology has focussed on the direct application of
biochar in soils for the accounted benefits. This strategy still has a huge
impact on the cost of investments and production processes which stands as a
major challenge in adopting the use of biochar.   Secondly, another problem preventing a
universal adoption of biochar application is to tailor a single biochar with a
soil and crop type, which is since biochar content in nutrients and properties
for the same production conditions still vary with the type of biomass used.

Biochar production process has the capacity generates
biofuels (mainly methane and Hydrogen), and heat energy for sustainable
district heating all of which are more clean and renewable source of energy
compared to fossil fuels and other heat sources like that obtained from
incineration. One major challenge still faced by both developed and developing
nations is the sustainable management of organic waste when considering global
trends and responds to strategies put in place via international and national
frameworks 2 In response to such frameworks, this reports
considers biogas and biochar production processes as a synergistic and  appropriate strategy for the management of
organic wastes which can help in the mitigation of climate change indirectly by
recovering energy from waste, reducing industrial energy use and emissions due
to recycling and  reduction of waste,
decreasing methane emissions from landfills, decreasing energy used in long
distance transport of waste (one major problem in Swedish biogas industrial
sector), and enhancing C sequestration in forests due to decreased demand in
virgin paper in the paper and pulp industry.  

Biochar is a carbonaceous material obtained from
biomass pyrolysis or gasification process. Biochar has long been used as one of
the alternatives to the non-environmentally friendly and expensive chemical
fertilizers. Previous findings have demonstrated numerous reasons for the use
of this product including its capacity to improve soil fertility, immobilize
trace metals, recycle nutrients, retains water in the soils thereby minimizing
leaching and reducing the cost of water use for irrigation (especially in the
tropics and arid regions) as in ­ 1 It
also stabilizes soil pH and contributes in the reduction of greenhouse gases
like Carbon dioxide and Methane via carbon negative sequestration processes.