Page 119 - Sustainable Cities and Communities Design Handbook

96 Sustainable Cities and Communities Design Handbook

biomass in conventional power plants can simultaneously scale up the use of
biopower and mitigate the environmental impacts of fossil fuel combustion.
Gasification systems and organic, anaerobic digestion can also be used to
convert biomass into syngas (a mixture of carbon monoxide and hydrogen gas)
and methane, respectively. Biomass-derived gases can be used in high-
efficiency combined cycle generators and other modular systems, making
them prime distributed generation devices.
The broad distribution of resources and diversity for utilizing them makes
biomass a viable renewable energy source for much of the contiguous United
States. It is a particularly important renewable resource in the southeast, which
has a modest endowment of solar, wind, and geothermal resources. A survey of
available biomass resources from forest and agricultural lands determined that
the technically and economically exploitable volume of biomass is more than
seven times greater than the current usage rate (Estimating Renewable Energy).
Transportation costs and seasonal availabilities diminish the attractiveness of
biomass as an energy resource, particularly in electricity markets, where it
competes with coal’s low costs and all-year availability.
In 2015, Americans consumed 3.9 quads of biomass-based energy (Short-term
Energy Outlook, 2017), about 4% of the total energy used in the United States
that year. Woody biomass and wood by-products account for 52% of the
energy content of biomass feedstocks and is used primarily for electricity
production and industrial heating. Ethanol and biodiesel make up 35% of the
biomass total, and combusted agricultural and municipal solid wastes supply
most of the biomass balance. Taken together, these three sources of energy
provide two-fifths of the renewable energy consumed in the United States.
Some 17,300 MW of currently installed electricity-generating capacity has
some form of biomass as its primary feedstock (Preliminary Monthly, 2017).
In 2015, 64 TWh of biopower electricity were produced, half of which was
produced outside of the electric power sector (Electric Power Annual, 2015).

MARINE AND HYDROKINETIC
In oceans and rivers exist large, regular, and untapped ebbs and flows of water.
The technical resource potential of these energy sources is substantial, sum-
ming to as much as 750 TWh per year (Quadrennial Technology Review,
2015).
There are three potential categories of marine and hydrokinetic energy
(MHK) resources: waves, tides, and river and ocean currents. As a whole, the
MHK energy industry is in the early stages of development, and although there
is a broad array of concepts and designs for capturing marine energy, there has
been relatively little in the way of deployment or standardization, particularly at
the commercial level. As of this writing, there are no commercial MHK systems
operating in the United States (Quadrennial Technology Review, 2015).