Renewable Energy from Urban Landscapes.

Utilizing biomass from urban landscapes could significantly contribute to the nation’s renewable energy needs.  In 2007, an experiment was begun to evaluate the biomass potential from a bermudagrass, Cynodon dactylon var. dactylon (L.) Pers., lawn in Woodward, OK and to estimate the potential biomass yield for the City of Woodward.  Woodward has a population of nearly 12,000 people and 10% of its total land area (3,560 ha) is estimated to be in lawns.  On 15 April, a lawn was thatched and fertilized with 50g m^-2 of 13-13-13 (N-P-K).  Mowing began on 18 May and every 10-14 d thereafter.  The potential yield was estimated by harvesting four 1 x 16 m areas.  The harvested material was weighed fresh, a 250- to 300g subsample was collected and dried, and percentage dry matter was determined.  The total DM of each sample was calculated by multiplying the percentage DM of the oven-dried sample by the harvested green weight of the sample.  In addition, fallen leaves and tree limbs, tree limbs from pruning operations, and tree removal were recorded, weighed, and converted to DM and added to the lawn estimates for total annual biomass potential.  Estimates for 15 April-22 September showed that a lawn could yield 525 kg of DM (equivalent to 11.9 Mg ha^-1).  Of this yield, 225 kg were carbon and 17 kg were nitrogen.  It was also estimated that 3,720 Mg of biomass could be collected annually from the City of Woodward if every homeowner collected their lawn clippings.  If additional components, like fallen leaves, tree limbs, tree limbs from pruning operations, and tree removal, were added to the lawn biomass, a total about 860 kg (19 Mg ha^-1) of DM would be available for alternative energy.  The City of Woodward could produce an estimated 6,150 Mg of annual biomass DM containing 2,725 Mg of carbon and 155 Mg of nitrogen.  Biomass from urban landscapes is an untapped resource.  Research using other turf grass species in difference regions of the USA should be conducted to fully understand their potential for renewable energy.