Page 320 - Advances in Eco-Fuels for a Sustainable Environment

Thermal depolymerization of 10

biogas digestate as a viable
digestate processing and resource

recovery strategy

*
*
Oseweuba Valentine Okoro , Zhifa Sun , John Birch †
*Department of Physics, University of Otago, Dunedin, New Zealand
†
Department of Food Science, University of Otago, Dunedin, New Zealand

10.1 Introduction

It is now widely accepted by the scientific community that proven global fossil
reserves cannot sustainably satisfy the growing global demand for fossil-sourced
energy. This is because not only are these reserves fixed and nonrenewable, but also
the utilization of these fossil reserves results in the generation of unwanted greenhouse
gas emissions such as SOx and NOx , which are considered largely responsible for the
predicted future climate-related catastrophes. The depletion of fossil reserves is fur-
ther exacerbated by the projected increase in worldwide energy consumption, which
will surpass 650 EJ by 2025 and from year 2025, increase geometrically by a factor of
1.4 over the next 25years [1]. In addition to issues associated with the depletion of
fossil reserves, the rate of global organic waste generation constitutes another chal-
lenge with which our society is currently contending [2]. This is because global
wastestreams are composed of about 50% organic content, translating to an organic
stream generation rate of 3megatons per day [2]. These organic wastestreams have
the capacity to generate unwanted greenhouse gases during uncontrolled decay and
degradation processes [2]. Crucially, the combined negative effects of the depletion
of nonrenewable fossil reserves and the generation of large masses of organic
wastestreams are expected to be exacerbated by the anticipated increase in global pop-
ulation, leading to an associated increase in both global energy demand and global
organic waste generation rates.
In an attempt to manage the large masses of organic waste and also enable cheap
bioenergy production as a strategy for reduced fossil energy dependence , the waste
management industry has in recent times extensively explored anaerobic digestion
technologies for both solid and liquid waste processing. According to De Baere
[3], anaerobic digestion (AD) technologies currently constitute up to 25% of all bio-
logical treatments in Europe because AD technologies provide a cheap pathway for
bioenergy generation from degradable organic wastestreams via oxygen-free degra-
dation of organics for biogas production. The utilization of the AD technologies,

Advances in Eco-Fuels for a Sustainable Environment. https://doi.org/10.1016/B978-0-08-102728-8.00010-3
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