A: Renewable energy is being interpreted very broadly these days,
with both the nuclear industry trying to don the label and certain State
portfolio standard definitions which include coal bed methane and deep
well gas. In federal DOE programs, hydrogen made from natural gas and coal
is being "spun" as renewable as are supposed 'clean' coal technologies.
The core renewable energy technologies -- biomass, geothermal, hydropower,
solar and wind -- are generally non-controversial, except certain
environmental groups try to contain these, especially larger hydropower
and certain biomass resources, from time-to-time.
The two technologies that fall into definitional limbo are 'waste heat'
known as either 'cogeneration' or more recently as 'combined heat and
power' (chp) - zero emission electricity and thermal energy from existing
processes. Trash plants -- or what we usually call conventional
incinerators -- have been trashed (pun intended) by the environmental
community because these mixed wastes have heavy metals and carcinogenic
compounds that get dispersed in the air and water. Newer 'direct burn'
technologies at exceedingly high temperatures and pressures seem to
address many of these concerns. But the prevailing approach is to 'source
separate' metals, plastics, chemically-treated wood (i.e. demolition) with
solid enforcement mechanisms for recycling and then either utilize the gas
(landfill gas) or combust the organic wastes for electricity -- a much
more benign approach.
The biorefinery advocates go a step further and not only support generic
recycling and energy production for heat and electricity, but also create
a broad set of bioproducts which include building and roadway materials,
fertilizers, pet litters, paints, and glues and resins - just to name a
few co-products. The old saying that "one person's waste is another's
treasure, is surely true. And I personally support waste heat and
waste-to-energy, done in the most efficient, sustainable processes with
strict local enforcement to ensure environmental compliance, as within the
renewable energy definition.