A toxic purple haze of diesel exhaust hangs over the rice and jute fields here in northern India, and bird songs are frequently drowned out by the chug-a-chug-a- chug of diesel generators. Across the developing world, cheap diesel generators from China and elsewhere have become a favorite way to make electricity. They power everything from irrigation pumps to television sets, allowing growing numbers of rural villages in many poor countries to grow more crops and connect to the wider world.