Life Cycle Costs and Life Cycle Assessment for the Harvesting, Conversion, and the Use of Switchgrass to Produce Electricity

This paper considers both LCA and LCC of the pyrolysis of switchgrass to use as an energy source in a conventional power plant. The process consists of cultivation, harvesting, transportation, storage, pyrolysis, transportation, and power generation. Here pyrolysis oil is converted to electric power through cocombustion in conventional fossil fuel power plants. Several scenarios are conducted to determine the effect of selected design variables on the production of pyrolysis oil and type of conventional power plants. The set of design variables consist of land fraction, land shape, the distance needed to transport switchgrass to the pyrolysis plant, the distance needed to transport pyrolysis oil to electric generation plant, and the pyrolysis plant capacity. Using an average agriculture land fraction of the United States at 0.4, the estimated cost of electricity from pyrolysis of 5000 tons of switchgrass is the lowest at $0.12 per kwh. Using natural gas turbine power plant for electricity generation, the price of electricity can go as low as 7.70 cent/kwh. The main advantage in using a pyrolysis plant is the negative GHG emission from the process which can define that the process is environmentally friendly. 1. Introduction Our dependence on fossil fuel has increased over the past century due to increasing energy consumption. The U.S. Department of Energy [1] stated that transportation energy demand is increasing at an annual rate of 0.2 percent from year 2010 to 2035. Total electricity consumption is also increasing at an annual rate of 0.8 percent from 3879 billion kilowatt-hours in 2010 to 4775 billion kilowatt-hours in 2035. On the other hand, the world oil reservoir is decreasing. From BP’s estimates [2], world oil production has already reached its maximum and is expected to drop. At the present production rate, the world oil reservoir will last for forty-one years. Renewable energy such as biooil will be an alternative source to make up the reduction of oil production rate. Faaij [3] reported that fossil fuel dominated the world’s energy uses, supplying 80% of the total energy requirement. However, 10–15% of this demand could be covered by biomass resource. Biomass is an important energy resource for developing countries accounting for 50–90% of their total energy requirement. Advantages of biomass energy include potential to reduce GHG emissions, substitution for depleting global crude oil reservoir, potential impacts on waste management, and the conversion of waste resources into clean energy. Waste resources include natural forests wood,