Environmental Engineering Reference
In-Depth Information
in the evenings (or when clouds block sunlight) the grid returns electricity to the
homes, enabling net metering of the electricity consumed.
Smart grids capable of wireless network communication can also replace manu-
al electricity meters.
The conversion of sunlight into chemical energy supports nearly all plant and an-
imal life on Earth. It is estimated that 20 billion tons of carbon are stored per year
by photosynthesis in terrestrial plants and another 13 billion dry tons in oceanic
plants. Biomass is one of humanity's oldest energy resources, and it still accounts
for approximately 10% of global primary energy consumption today. As much as
one-third of the world's population relies on fuel wood, agricultural residues, an-
imal dung, and other domestic wastes to meet household energy needs. Such tradi-
tional uses of biomass are estimated to account for more than 60% of the biomass
contribution to global energy supply, most of which occurs outside the formal mar-
ket economy and predominately in developing countries. Modern uses of biomass
to generate electricity and heat or as a source of fuels for transportation are estim-
ated to account for less than 40% of total biomass energy consumption worldwide.
Modern uses of biomass, however, offer a far greater array of possibilities for
reducing dependence on fossil fuels, curbing greenhouse gas emissions, and pro-
moting sustainable economic development. A range of biomass energy technolo-
gies, suitable for small- and large-scale applications, are available. They include
gasification, combined heat and power (cogeneration) schemes, landfill gas, en-
ergy recovery from municipal solid wastes, or biofuels for the transportation sector
(ethanol and biodiesel). Recent interest in biomass energy has focused primarily on
applications that produce liquid fuels for the transportation sector. Given growing
concerns about global petroleum supply and the current lack of diversity in avail-
able fuel options for the transport sector, such fuels represent the highest-value use
of biomass energy at present. Ultimately, the most promising biomass applications
of all are likely to involve integrated systems where, for example, biomass is used
as both fuel and feedstock in the coproduction of liquid transportation fuels and
electricity.
