Previously this site covered microbial fuel cells. Waste water fuel cells can produce 18 watts per 260 gallons of water and achieved a charge efficiency of more than 70 percent.
Lesser developed countries discharge approximately (the equivalent of) 100 trillion gallons (380×10**9 m³) of untreated sewage per annum. This could potentially generate 7 Terawatts of power for them and clean up their waste water.
These kinds of approaches plus a lot more nuclear power and shifting to more electrical transportation (hybrids and all electric.)can be used to blunt peak oil.