Tax credits would go to companies that convert chicken droppings into electricity under a provision tucked into a giant Senate tax-cut bill by Sen. William Roth (R-Del.). Chicken farming is the largest agricultural enterprise in Delaware, and chicken manure has become a major source of pollution. Technology for burning the manure to produce electricity has long existed but never been profitable. Rep. Bill Archer (R-Texas), head of the House Ways and Means Committee, will likely fight the measure because chicken droppings could compete with oil and gas.