Production Processes:
The production process of biodiesel from algae is a simple process that consists of four steps:
- Growth
- Harvest
- Extraction
- Conversion
Growth & Harvest:
Algae growth require sunlight, carbon-dioxide and water. Photosynthesis is an important bio-chemical process in which plants, algae, and some bacteria convert the energy of sunlight to chemical energy.
The existing large-scale natural sources are of algae are: bogs, marshes and swamps - salt marshes and salt lakes. Micro-algae contain lipids and fatty acids as membrane components, storage products, metabolites and sources of energy. Algae contain anything between 2% and 40% of lipids/oils by weight.
Tubular Photobioreactor and Raceway ponds are the main equipments used to grow harvest algae. They can be set up to be continually grow and harvest (like the majority of the larger cultivation systems), or by growing and harvesting a batch at a time (like polyethylene bag cultivation). A batch photobioreactor and Raceway ponds are set up with nutrients and algal seed, and allowed to grow until the batch is harvested. A continuous photobioreactor and Raceway ponds are harvested, either continually, as daily, or more frequently.
The existing large-scale natural sources are of algae are: bogs, marshes and swamps - salt marshes and salt lakes. Micro-algae contain lipids and fatty acids as membrane components, storage products, metabolites and sources of energy. Algae contain anything between 2% and 40% of lipids/oils by weight.
Tubular Photobioreactor and Raceway ponds are the main equipments used to grow harvest algae. They can be set up to be continually grow and harvest (like the majority of the larger cultivation systems), or by growing and harvesting a batch at a time (like polyethylene bag cultivation). A batch photobioreactor and Raceway ponds are set up with nutrients and algal seed, and allowed to grow until the batch is harvested. A continuous photobioreactor and Raceway ponds are harvested, either continually, as daily, or more frequently.
Raceway pond:A raceway pond is usually made of a closed loop channel that is 0.3 m deep. A paddlewheel is used to keep the circulation in the channel going. A raceway pond channels are built in concrete, or compacted earth, and maybe lined with white plastic to collect sunlight during daytime. Broth is harvested before the paddlewheel after the circulation loop is completed. The paddlewheel operates all the time to prevent sedimentation. Raceway ponds have been used since 1950s. The Largest raceway based biomass facility occupies an area of 440,000 m^2.
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Photobioreactors:Photobioreactors consists of arrays of straight tubes, they are usually 0.1 m or less in diameter because light does not penetrate too deeply in the broth. The limited diameter is meant to increase the biomass productivity of the photobioreactors.
The Tubes are always oriented North-South in order to maximize the sunlight captured by the solar collector. In a typical arrangement, the solar tubes are placed parallel to each other and flat above the ground. Horizontal, parallel straight tubes are sometimes arranged like a fence, in attempts to increase the number of tubes that can be accommodated in a given area. |
Raceway Ponds vs. photobioreactors
Both Photobioreactors and Raceway ponds are very effective way of algae growth and harvesting; however, photobioreactors are more efficient and productive than the Raceway ponds. Table 3 shows the comparison between photobioreactor and raceway production. By fixing the annual biomass production to 100,000 kg, it is clear that photobioreactors are more productive than raceway pond in every aspect. However, when it comes to cost, raceway ponds are way cheaper to set up and maintain than photobioreactors.
Extraction & conversion:
Extraction comes after the harvesting where the biomass collected is being used to produce oil. Extraction is a simple process which involve applying energy in order for the biomass to turn into oil (see image 2). In image 2 the algae is being inserted into an extraction tank and applying an electromagnetic fields to get rid of any impurities. A further step is taken by inserting the solution from the extraction tank to a gravity clarifier, where the lipid (desired oil) get separated from the biomass. This oil then is being converted to biodiesel, and the biomass is being recycled back to the growth step where it can be reused to produce more algae.
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During conversion, a chemical process known as “transesterification” is used to modify the carbon chains into the structure desired. The transesterification process “involves adding alcohol in a base mixture to convert the triglycerides into three smaller hydrocarbon chains to make an alternative fuel for diesel engines.” Another product is “Glycerin,” which is taken and sold separately in order to reduce the cost of production. The cost of production of biodiesel mainly depends on the price of feedstock. “According to industry data, a five-million gallon per year biodiesel conversion plant (14,000 gallons per day) would have cost approximately $6,500,000 in 2005 or about $7,300,000 in 2009 dollars.” Another major issue is that the research assumed that the capital cost was available at no cost, and some of the materials were available at no cost as well (CO2).
After discussing the production processes of biodiesel, now comes the most important question "How much will it cost?" The reason of choosing petroleum diesel over biodiesel in the first place was that the cost of production of petrodiesel was cheaper than biodiesel back in the days; however, with the new technology available nowadays we are able to fairly compete against petrodiesel prices. So it is time to discuss some of the financial involved in this project. Click here to continue...