It’s a no frills three-tank filtering system that turns waste oils into a sooty solvent which, when blended with regular diesel fuel, can be burned in unmodified diesel engines. The filtered fuel is called “black diesel,” an economically attractive and environmentally friendly product which backers contend has the potential to become black gold if used on a grand scale during times of high pump prices. TDCJ successfully tested the filtering system at the Eastham Unit near Lovelady last year and plans on installing it at five additional prison facilities this year.
Like the system itself, the steps in making black diesel aren’t complicated. Into one large cone-shaped tank go all of the used motor, hydraulic, gear and transmission oils taken from vehicles during routine maintenance. Allowed to settle for a couple of days so any solids or water can be drained off, the oils are pulled out of the first tank by an electric motor and pushed through two tightly woven filters to remove most of the remaining impurities before draining into a second tank. From the second tank it passes through an even finer filter and finally into a third, smaller tank containing regular diesel. And that’s pretty much it. After an additive is added, the mixture is aerated and then pumped straight into vehicles.
Kent, who oversees the agency’s farm equipment, cannery and crop production, said he proposed the pilot project at Eastham after becoming frustrated with the high price he was paying at the pump for diesel last summer. He, along with Eastham Farm Manager Mack Currie and Maintenance Supervisor Glenn Smith, used some salvaged parts to piece together the system and began burning black diesel in three tractors and a motor grader in late July. Just over 1,400 gallons of waste oil had been filtered through early December and approximately 1,300 gallons of the fuel mixture had been burned. The testers started with a 60-40 blend of filtered waste oil and regular diesel but switched to a 50-50 mixture in September. Kent said none of the equipment used in the six-month pilot project experienced mechanical problems while burning the fuel and that there was no discernable difference in mileage or performance. In fact, since black diesel burns hotter than regular diesel, he said the blend actually boosted horsepower in the equipment.
Building on its success at Eastham, Kent’s department plans to expand the waste oil filtering system to the Ramsey, Darrington, Ellis, Coffield and Hilltop units during the first six months of this year. The department is also exploring the feasibility of taking yellow grease waste from unit kitchens and turning it into pure bio-diesel. Initial study shows that TDCJ units produce approximately 300,000 gallons of yellow grease annually, enough to replace about one third of the regular diesel now consumed by unit farm shops each year.