Sustainable Urban Living: Green Solar Energy for Food and Biofuels Production - Design with the Desert: Conservation and Sustainable Development - page 419

Sunshine

CO 2

Algal biomass

Lipids
Protein
Carbohydrates

Nutrients
recycled
from waste
streams

Mixing

Recycle water and nutrients

FIGURE 24.4
Abundant agriculture—algae cultivation.

Algae evolved in millions of independent moist environments which created over 75,000
known species and possibly 10 million total species. 25 The plant grows in nearly every
ecosystem and offers a wide variety of nutrient profiles for its many hungry consumers.
Algae are at the base of the food chain and serve as food for 100 times more organisms than
any other plant on Earth. Multiple algal species have adapted to every known ecosystem
on Earth but many prefer heat, sunshine, and brackish water.
Algae are far more productive than other biofuels sources because algae do not put
energy into producing roots, stems, trunks, and leaves because they grow in water. Algae
are energy positive because the energy cost of algaculture and downstream processing
is less than the energy yield of the algae oil, which is produced using solar energy in the
process of photosynthesis. The energy produced, clean, green diesel or jet fuel, provides
about 30% more energy than gasoline and about 50% more than ethanol. 26
Algae's energy potential is 30-100 times higher than corn ethanol production per
acre and algae's productivity advantage for protein is similar. Other parameters such as
coproducts, growing requirements, and ecological footprint may be even more critical
to the choice of changing to sustainable algaculture than oil productivity differences.
Algae's potential remains theoretical because scaled production has not yet been achieved.
However, significant production breakthroughs are occurring now. 27

24.7 Green Solar Geography
The ecology of the West and Southwest are ideal for algal production (Table 24.3). These
regions offer the unique combination of sunshine, warm weather with few frosts, and
low-cost flat, noncropland. The Southwest has numerous brine aquifers with water that
cannot support agriculture but are ideal for algae production.