Widescale Biodiesel Production from Algae

[Guest guest]

Based on a report by the US DOE and USDA entitled " Life Cycle

Inventory of Biodiesel and Petroleum Diesel for Use in an Urban Bus " 5,

biodiesel produced from soy has an energy balance of 3.2:1. That means

that for each unit of energy put into growing the soybeans and turning

the soy oil into biodiesel, we get back 3.2 units of energy in the

form of biodiesel. That works out to an energy efficiency of 320%

(when only looking at fossil energy input - input from the sun, for

example, is not included). The reason for the energy efficiency being

greater than 100% is that the growing soybeans turn energy from the

sun into chemical energy (oil). Current generation diesel engines are

43% efficient (HCCI diesel engines under development, and heavy duty

diesel engines have higher efficiencies approaching 55% (better than

fuel cells), but for the moment we'll just use current car-sized

diesel engine technology). That 3.2 energy balance is for biodiesel

made from soybean oil - a rather inefficient crop for the purpose.

Other feedstocks such as algaes can yield substantially higher energy

balances, as can using thermochemical processes for processing wastes

into biofuels (such as the thermal depolymerization process pioneered

by Changing World Technologies). Such approaches can yield EROI values

ranging from 5-10, potentially even higher.

 

Source:

http://www.energybulletin.net/2364.html