Environmental Engineering Reference
In-Depth Information
which is predicted to increase to 3 billion t by 2025 with increasing urbanization.
The production of fruit and vegetable waste is also very high and is becoming a
source of concern in municipal landfills because of its high biodegradability. The
potential sources of material for biomass energy are thus significant.
Our research on the urban water environment and bioenergy focuses on clean
and renewable energy, solid waste management, wastewater treatment and urban-
ization. In the area of wastewater treatment, we focus on the use of commercial and
novel membrane processes and investigate the performance and enhancement of
lab-scale wastewater treatment using novel membrane bioreactors and the Up-flow
Anaerobic Sludge Blanket Reactor (UASB). This chapter provides an overview of
the current state and future prospects for related biomass energy technologies based
on wastes as feedstock.
8.2
Biomass Sources and Waste
The term 'biomass' refers to organic substances that have stored energy through the
photosynthesis process, and is one of the most abundant and well-utilized sources
of renewable energy in the world. Biomass can be classified as in Fig.
8.1
accord-
ing to whether they are dry, moist or 'other' which includes a number of wastes.
The processes used for its utilization in terms of power generation or transport
fuels include direct combustion, biochemical conversion and thermo-chemical
conversion.
In Japan, around 322 million t of biomass is produced annually. Although the
biomass recycling rate is 76 %, the remainder is not recycled and can be regarded as
waste of which the largest sources are sewage sludge, waste paper, food waste, non-
edible agricultural products and forest residues. Material flows for 2006 are shown
in Fig.
8.2
and include a number of major sources which can potentially be used to
produce hydrogen or methane through biological processes.
8.3
Bio-hydrogen Fundamentals and Technology
8.3.1
Background
Hydrogen is used for chemicals and electronic devices production, hydrogenated
fats and oils in the food industry, steel processing and desulfurization, and reformu-
lation of gasoline in refineries. In addition, much research and development is un-
derway on using hydrogen in transport with terms such as 'the hydrogen economy'
widely used. However currently, over 95 % of the 50 million t of hydrogen produced
annually worldwide is from fossil fuels, so that its use makes little contribution to
reducing CO
2
emissions.