The Small-Scale Solution

Overview of the Technology

There are numerous ways of producing biodiesel from WVO or cold-pressed oilseed feedstock. Systems can range from solutions using an old oil barrel to financially sophisticated $6,000 commercial units from Biodiesel Solutions.

While each of these systems can claim to partially transesterify waste oil into biodiesel, none of the examples outlined can ensure that the biodiesel produced will meet the fuel quality requirements of ASTM standard D 6751. Nor do these systems address the issues of toxic waste streams that are a byproduct of the fuel production process, chemical handling safety, or environmental sustainability.

The small-scale technology solution described in Biodiesel Basics and Beyond represents improvements in the areas of fuel production, quality control, chemical and process safety, procedural development, and waste stream processing that have to date been sadly lacking in systems currently in use.

In keeping with the mandate of this book, which is to rigorously avoid the propagation of any myths or misinformation, statements of fact or results from specific tests have been analysed using proper scientific methods or third-party test equipment or laboratories to verify results and improvements over past efforts. Any areas of concern that remain have been catalogued and placed in the summary section, inviting further discussion and development.

The Production Facility

When Lorraine and I designed our off-the-electrical-grid home, we decided to add a small workshop area in the detached garage to house the biodiesel production facility. This extra space is located behind the door shown in Figure 8.1-1 and consists of an area of approximately 6 x 18 feet (1.8 x 5.5 meters). The room is well insulated and tightly sealed with standard construction-grade vapour barrier and acoustical gap sealant and is fitted with a ventilation fan that is capable of drawing approximately 500 cubic feet (14 cubic meters) of air from one end of the room to the other per minute of operation. The high-volume turnover air rate is required to keep methanol vapors to an absolute minimum, certainly below the lower explosive limit (LEL), as well to ensure that air quality remains high and nonpoisonous.

The production lab is shown in an overview image in Figure 8.1-2. All of the production equipment is mounted along the left wall, while the “wet laboratory,” safety equipment, and storage area are located along the right wall. This image shows, starting at the bottom left corner, the first tank which receives the WVO and is used to filter, dry, and deacidify the oil to desired standards. The second tank is the main reaction tank which performs the chemical conversion (transesterification) of WVO into biodiesel. It is also used to separate the raw biodiesel from glycerol and to recycle the excess methanol prior to washing the biodiesel.

The next small white conical tank is the chemical mixer which combines the methanol stored in the adjacent tank with a powdered catalyst forming sodium (or potassium) methoxide, which is pumped into the main reaction tank to start the conversion of WVO into biodiesel.

The small white tank beside the methanol is the biodiesel wash water storage tank. It contains a submersible heater which warms the wash water to 60°C prior to spraying it into the raw biodiesel which is stored in the large white conical wash tank. The wash tank is fitted with both water spray nozzles and an air bubbling system which are used to remove contaminants from the raw biodiesel.

The last tank visible at the far rear of the picture (located behind the large conical wash tank) is the biodiesel dryer. This unit removes any remaining water from the biodiesel before final filtration and storage.

Also visible in this image is the ventilation fan located along the rear wall and the electrical subpanel which provides electrical circuit control and protection for each of the process tanks, pumps, and heaters used in the system.

Running along the right sidewall is the wet lab area which is used to analyze both the WVO and the biodiesel produced by the system. The storage cabinets include all of the necessary process chemicals as well as test equipment, scales, and measuring beakers.

Safety is of primary importance when handling any chemicals and a variety of smocks, eye protection, rubber gloves, and spill cleanup materials as well as an eyewash station and multiple fire extinguishers are provided.

The photograph in Figure 8.1-3 was taken from the rear of the production lab, showing how all of the equipment and lab facilities fit neatly into this compact area. Note that the WVO receiver tank and the main reaction tank are lifted off the floor on a horizontal storage cabinet. In addition to providing additional storage space, the cabinet also houses a small reverse osmosis water filtration unit which feeds mineral-free water to the biodiesel wash tank.

The small black box mounted above the main reaction tank is the air-to-liquid heat exchanger which is used to condense methanol vapors driven off from the biodiesel reaction process. The unit operates as a fan-driven cooling unit, causing methanol vapor to condense and drip into the storage tank located next to the reaction tank. Condensed methanol is returned to the methanol storage tank for future use.

Because of the inline design of the production system, it is possible to simultaneously process approximately four 40-gallon (≈ 150 liter) batches of biodiesel at one time, with one batch in each stage:
• drying and deacidification of WVO
• transesterification of WVO into biodiesel along with methanol recovery
• washing of raw biodiesel
• drying of biodiesel prior to testing and storage

Processing of waste stream glycerol and wash water are handled “offline” and will be discussed in later chapters.

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