The City of Durango, TX stopped using biodiesel in its fleet because engines were becoming contaminated with an unidentified sludge, reports The Durango Herald. At a business luncheon, Hope Bleeker, Durango transit manager, said a city director had sent a sample of the sludge to a lab for analysis in the hope of resolving the problem. Bleeker said that 40,000 to 41,000 gallons of the 42,000 gallons of fuel used by the city last year were biodiesel, but the fleet has since gone all diesel.Bleeker mentioned other fuel alternatives such as ethanol and hydrogen fuel cells. She said the city is looking at using E85 ethanol in the near future, but noted no buses currently in the fleet could run on it. Hydrogen is too far off.Jeff Berman, project manager for the San Juan Biodiesel Cooperative, said these problems are often the result of lack of quality control in biodiesel production. Berman's organization is working to create a local biodiesel production facility, which would allow for better quality control. City Manager Bob Ledger said he is not rejecting biodiesel, but putting it on hold to smooth out problems and determine if it’s economically feasible, the Herald reports.