Diesel from Algae
The first thing we should do in a discussion of biodiesel is get rid of the word “biodiesel”. It implies that some varieties of diesel are made from organic matter and some are not. That is not true. Most diesel is made from crude oil, which is organic in its origin. So we should just throw out that term and consider ways to make diesel from substances other than crude oil.
It would take a book (a large book) to explore all the ways diesel can be made, so we will cover just one possible source here, algae. Algae? Diesel from pond scum? That is correct. Some varieties of algae are as much as 50% fat, and the fat is what you want.
In climates that are warm year-round, the algae can be grown outdoors, in large, shallow ponds. They can be very shallow because the algae only grow in the top one inch or so of the water. They need lots of sunlight and a hard freeze will usually kill the algae. Most of the commercial operations that have been built to harvest algae are in southern desert regions. It is simple to grow and maintain. Basically, the algae feed off of carbon dioxide and sunlight. An ideal location would be close to a power plant or a brewery or some similar facility that emits a lot of carbon dioxide. The carbon dioxide could be captured and used to nourish the algae rather than just being spewed into the atmosphere.
This should not be viewed as a method to reduce carbon dioxide emissions, however. The carbon dioxide is captured by the algae. The fat from the algae is converted into diesel. When that diesel is burned, the carbon dioxide goes into the atmosphere. The net gain in terms of carbon dioxide emissions is zero.
In colder climates, algae cannot be grown outside during the winter. Indoors facilities are fairly simple to build. A warehouse-type building filled with shallow trays would do the job. The trays would be loaded with algae on top of shallow, slowly moving water. The algae can be scraped off of the water at the end of the tray and the water returned for reuse.
Processing the algae starts with crushing it and squeezing all the water out of it. This process will recover about 70% of the fat. There are a variety of methods that can be used to recover more of the fat. Once the fat has been separated, it is loaded on a truck and sent to the refinery where it is processed into diesel. You have now succeeded in creating truck fuel out of pond scum.
