Skip to main content
Open Access Publications from the University of California


California Agriculture is a quarterly peer-reviewed journal reporting research, reviews and news on California’s agricultural, natural and human resources.

Volume 69, Issue 3, 2015

Woody Biomass: Energy, ecosystems, economics

Issue cover
Cover Caption: Complete contents, including news and editorial featuresTruck tippers empty chip vans filled with woody biomass to fuel the Buena Vista Biomass Power facility near Ione (Amador County). Photo by Will Suckow.

Research and Review Articles

Forest biomass diversion in the Sierra Nevada: Energy, economics and emissions

As an alternative to open pile burning, use of forest wastes from fuel hazard reduction projects at Blodgett Forest Research Station for electricity production was shown to produce energy and emission benefits: energy (diesel fuel) expended for processing and transport was 2.5% of the biomass fuel (energy equivalent); based on measurements from a large pile burn, air emissions reductions were 98%-99% for PM2.5, CO (carbon monoxide), NMOC (nonmethane organic compounds), CH4 (methane) and BC (black carbon), and 20% for NOx and CO2-equivalent greenhouse gases. Due to transport challenges and delays, delivered cost was $70 per bone dry ton (BDT) — comprised of collection and processing ($34/BDT) and transport ($36/BDT) for 79 miles one way— which exceeded the biomass plant gate price of $45/BDT. Under typical conditions, the break-even haul distance would be approximately 30 miles one way, with a collection and processing cost of $30/BDT and a transport cost of $16/BDT. Revenue generated from monetization of the reductions in air emissions has the potential to make forest fuel reduction projects more economically viable.

Effects of fuel treatments on California mixed-conifer forests

Land managers implement forest fuel reduction treatments, including prescribed fire, mastication, and hand- and mechanical thinning, to modify wildfire behavior. Fuel treatments decrease tree density, increase mean canopy base height and remove surface fuels, and have been shown to reduce fire severity in yellow pine and mixed-conifer forests, even under relatively severe weather conditions. However, less is known about the impacts of fuel treatments on other facets of forest ecology. Synthesizing evidence from the scientific literature regarding their effects on forest structure, carbon, vegetation, soils, wildlife and forest pests, we found a developing consensus that fuel treatments, particularly those that include a prescribed fire component, may have neutral to positive effects on a number of ecological processes in frequent-fire coniferous forests and may increase forest resilience to future disturbance and stress.

Thinning treatments had minimal effect on soil compaction in mixed-conifer plantations

If biomass utilization results in soil compaction and reduced forest productivity, the potential benefits may be considered to be not worth the long-term impacts. We analyzed soil strength, an indicator of soil compaction, prior to and following commercial thins (sawlog and biomass harvest) and mastication treatments in 24- to 30-year-old mixed-conifer plantations in the central Sierra Nevada. Soil strength in mature, untreated second-growth stands was also measured as a reference. Neither the commercial thins nor the mastication treatments resulted in statistically detectable increases in compaction. Most of the existing compaction came from the original regeneration harvest that established the plantations several decades earlier. It will be important to monitor repeat treatments and long-term effects, but this study suggests that managers should not expect large impacts from thinning treatments on soil compaction in forests such as the one studied here as long as best practices are used.

Modeling fuel treatment impacts on fire suppression cost savings: A review

High up-front costs and uncertain return on investment make it difficult for land managers to economically justify large-scale fuel treatments, which remove trees and other vegetation to improve conditions for fire control, reduce the likelihood of ignition, or reduce potential damage from wildland fire if it occurs. In the short-term, revenue from harvested forest products can offset treatment costs and broaden opportunities for treatment implementation. Increasingly, financial analysis of fuel treatments is also incorporating long-term savings through reduced fire suppression costs, which can be difficult to quantify. This paper reviews the findings and lessons from recent modeling work evaluating the potential relationship between fuel treatments and avoided fire suppression costs. Across studies, treatments are generally predicted to reduce future fire suppression costs, although the magnitude of savings is unlikely to fully offset fuel treatment costs. This funding gap highlights the importance of forest product revenues in facilitating landscape-scale treatment. Factors influencing the effects of fuel treatment investments on fire suppression costs include the causal pathway linking treatment inputs to suppression cost outcomes; the spatiotemporal uncertainty of wildfire-treatment interactions; and the scale of fuel treatment programs.

Economic sustainability modeling provides decision support for assessing hybrid poplar-based biofuel development in California

Biofuels are expected to play a major role in meeting California's long-term energy needs, but many factors influence the commercial viability of the various feedstock and production technology options. We developed a spatially explicit analytic framework that integrates models of plant growth, crop adoption, feedstock location, transportation logistics, economic impact, biorefinery costs and biorefinery energy use and emissions. We used this framework to assess the economic potential of hybrid poplar as a feedstock for jet fuel production in Northern California. Results suggest that the region has sufficient suitable croplands (2.3 million acres) and nonarable lands (1.5 million acres) for poplar cultivation to produce as much as 2.26 billion gallons of jet fuel annually. However, there are major obstacles to such large-scale production, including, on nonarable lands, low poplar yields and broad spatial distribution and, on croplands, competition with existing crops. We estimated the production cost of jet fuel to be $4.40 to $5.40 per gallon for poplar biomass grown on nonarable lands and $3.60 to $4.50 per gallon for biomass grown on irrigated cropland; the current market price is $2.12 per gallon. Improved poplar yields, use of supplementary feedstocks at the biorefinery and economic supports such as carbon credits could help to overcome these barriers.

Are double trailers cost effective for transporting forest biomass on steep terrain?

Transportation of forest biomass on steep terrain involves logistical challenges. Trucks with large single trailers are often unable to travel on forest roads due to their narrowness, tight curves, adverse grades and limited areas to turn around. A shorter trailer must be used but then transportation capacity is limited by the trailer volume due to the low bulk density of the processed biomass, particularly when the biomass is dry. With double trailers, transportation capacity can be limited by allowable legal weight based on axle number and spacing. We developed a simulation model that explores the economic feasibility of using double-trailer configurations to transport forest biomass to a bioenergy facility from the grinder at a landing or from a centralized yard in Washington, Oregon and California. Results show that double trailers can be a cost effective alternative to single trailers under limited conditions in Oregon and Washington, but they are not a competitive option in California due to the state's transportation regulations.

Biomass power plant feedstock procurement: Modeling transportation cost zones and the potential for competition

Transportation of comminuted (processed) woody biomass from the production site to a utilization point is one of the most costly operational components in feedstock procurement. This study identified potential sources of feedstock based on transportation cost from which three woody biomass power plants in Humboldt County, California, could economically obtain their supply. We conducted service area and location-allocation network analyses for timberlands and sawmills, respectively, and created inclusive and exclusive networks to model three transportation cost zones (TCZs). The area within the $20/bone dry ton TCZ had the highest potential supply of woody biomass in the county (709,565 acres). All sawmills in the county were within an economically viable distance of the power plants. Even though there was no competition for raw materials at the time of this study, a competition risk analysis suggested that this could change with shifts in the demand for biomass or the price of electricity. The methods we developed for this study could be adapted to other regions with managed timberlands and a strong forest products industry.

California's agricultural regions gear up to actively manage groundwater use and protection

New regulations are emerging in response to historic groundwater depletion and widespread groundwater quality degradation in California. They aim at long-term preservation of groundwater resources for use in agriculture, in urban areas and for the support of ecosystems in streams dependent on groundwater. The regulations are driving a historic shift in the way the agriculture sector is engaged in managing and protecting groundwater resources in California. A review and synthesis of these recent regulatory developments — the Sustainable Groundwater Management Act and new policies under the California Porter-Cologne Water Quality Control Act — clarifies key challenges for farmers, scientists and regulators and points to the need for continuing innovation in agricultural practices as well as in planning and policy.