After sustainable forest management or logging, piles of forest residue, or slash, are produced within the forest. Forest slash resources are currently a wasted renewable fuel resource that could help California meet renewable portfolio standard goals. Also, forest slash piles represent a significant fire hazard, and are sources of greenhouse gas emissions and pollutants, if simply burned in piles. To mitigate these impacts and increase renewable energy production, a novel and modular Forest Power (FORPOWER) system was developed to convert forest slash to power at an economically viable cost under California Senate Bill (SB) 1122 (Rubio, Chapter 612, Statutes of 2012). The modular power system integrates a simple biomass feeder, doesn’t require a syngas cleaner, and uses a compact novel heat exchanger and commercial gas turbine, which results in lower system costs versus conventional systems. In addition, a novel biomass densification system module that compacts slash into logs was developed to reduce forest slash delivery costs to the power module.
The goal of the project was to show how the FORPOWER system, which includes the densification module, supports SB 1122 by cost-effectively converting forest slash to electric power at distributed locations throughout the state close to forest resources. Pilot-scale system biomass test results and analyses under the project showed that an acceptable 4.6- year simple payback could be achieved for a 5 MWe full-scale combined heat and power FORPOWER system, demonstrating the economic viability of the system. In addition to economic benefits, implementing 28 FORPOWER bioenergy modules could reduce greenhouse gas emissions by 1 million tons per year. The gaseous emissions and exhaust opacity from the test system were below San Joaquin Valley Air Pollution Control District regulated limits for biomass boilers. Implementing these environmentally acceptable systems in California would support renewable power standards, reduce the risk of forest fires, and improve forest sustainability.
