Urban Biomass-Not An Urban Legend.

Utilizing biomass from urban landscapes could significantly contribute to the nation’s renewable energy needs.  There is an estimated 16.4 million hectares of land in urban areas cultivated with turfgrass and associated vegetation.  Vegetation in urban areas is intensely managed which lead to regular pruning and clipping.  Lawn clippings, fallen leaves and tree limbs are all potential sources of biofuels.  Cities could collect and transport biomass materials to a local conversion plant where it could be used to produce alternative energy.  In 2007, an experiment was begun to evaluate the biomass dry matter (DM) potential from a bermudagrass, Cynodon dactylon (L.) Pers., lawn and associated vegetation in Woodward, Oklahoma and to estimate the potential biomass yield for the City of Woodward. Each year in April, the lawn was dethatched and fertilized.  Mowing began in mid-to-late May and biomass DM yield was estimated by harvesting four 1 x 16 m areas.  In addition, the DM yield of fallen leaves and tree limbs from prunings operations added to the lawn yield estimates for total annual biomass potential.  These data suggest that during a high precipitation year, it was possible to harvest from 13.5-to-19.0 Mg of DM biomass per hectare from an urban landscape and 8.0-to-12.3 Mg of DM biomass per hectare are possible for years with normal precipitation.  It was estimated that the City of Woodward could generate about 3,750 Mg of biomass DM in a normal rainfall year and about 6,100 Mg in a high rainfall year if every homeowner collected and offered for bioenergy production their lawn thatch, lawn clippings, tree leaves, and tree prunings.  On the basis of a 10 Mg ha^-1 DM annual yield, an estimated 164 million Mg of biomass DM could be collected in USA urban areas.