undigested sewage sludge, may pay a
district energy facility to accept it. There
are also disadvantages associated with
use or production of biomass fuel,
including challenges to the supply chain,
which may occur during pickup, transportation, off-loading, handling, storage
and processing. Certain biomass streams,
such as undigested sewage sludge, may
require specialized loading and transport
equipment. Some streams are available
in batches rather than continuously and
will have to be stored. As an example,
chicken litter is only collected from the
poultry barn every three to four months
between flocks.
Determining the feasibility of biomass
for a particular facility requires an analysis
of many technical, economic and environmental factors. First and foremost,
there must be local access to a reliable
source of a sufficient quantity of biomass
stream, and preferably, a homogeneous
biomass stream.
Technical and economic feasibility
also depend on the current technology
employed by the central plant and the
cost of equipment modifications, if any,
to accept biomass fuel. For example, a
coal-fired plant can directly burn wood
waste. However, a natural gas-fired plant
must be adapted to burn gas produced
from a biomass source, which has a
heating value of one quarter of natural
gas per cubic foot. Nozzles and other
components of the system must be
replaced with larger components to
accommodate the higher gas flow. Add
to that the cost to construct a gasification plant (or digester), if necessary, for
conversion of the available waste stream
into fuel gas.
These costs must be weighed against
the costs – and availability – of burning
natural gas. The decision also depends
greatly on environmental factors, including
state and local permitting regulations, as
well as public opinion.
There are always risks associated
with implementation of an emerging
technology, such as biomass energy.
District energy managers who understand
and accept the case against natural gas,
however, may find that the benefits of
biomass outweigh the risks.
Kevin Rhodes, PE, is project
director of the Energy Utilities Group
of Woolpert Inc., based in Cincinnati,
Ohio. Rhodes has more than 25 years
of experience in the energy and
construction industry, including
gas, oil, coal and nuclear plants. A member of
IDEA, Rhodes’s work includes extensive experience in planning, design and implementation
of district utility systems. This article is adapted
from his presentation given at IDEA’s 99th
Annual Conference & Trade Show. Woolpert’s
Energy Utilities Group’s clients include The
Pennsylvania State University, Duke University
and The Ohio State University. Rhodes can be
reached at kevin.rhodes@woolpert.com.
