With wildfires becoming more frequent and severe in North America and around the world, forest management plans have come under review in an effort to mitigate higher fire suppression costs as well as human and climate induced fire regime changes. When implementing forest management plans, small communities located deep within the wildland urban interface (WUI) are often left out of the equation for reasons largely to do with economies of scale. Yablecki et al. (2011) developed a comprehensive approach to treating fuels to minimize the threat of wildfires in remote areas while using the biomass generated from the forest treatment process for electrical generation, making the communities more sustainable and self-sufficient. Additionally this community-based model afforded long term lowered utility costs and greenhouse gas (GHG) emission reductions. The authors conclude that their proposition combines wildfire mitigation through forest treatment, power generation through use of biomass, and all other associated benefits, in a model that is entirely managed by the community. –Lindon Pronto
Yablecki, Jessica, Bibeau, Eric L., Smith, Doug W., 2011. Community-based model for bioenergy production coupled to forest land management for wildfire control using combined heat and power. Biomass and Bioenergy 35, 2561–2569.
Using previously published work and available information, Yablecki et al. established and presented a general understanding of the wildfire threats and range of energy (acquisition) needs, and coupled them with common fuels treatment processes and costs per hectare under forest management plans in the USA and Canada. An estimated 20, 000 communities have been identified in the US as vulnerable to wildfires, many of the most severely threatened and previously impacted, lying within the Wildland Urban Interface (WUI)—the area where communities integrate into forested land. In these areas there is less access (escape routes), more dangerous fuel loading in close proximity to homes, and in more remote areas, very limited fire suppression resources. This study postulates that reactive fire management plans are no longer effective, and that in addition to other factors, proactive fuel treatment is preferred to heighten public safety, reduce the high cost of fire suppression activities, and to limit the devastating effects of home and business loss. In more remote communities, the authors propose an all encompassing model to accomplish the aforementioned goals, through community involvement and innovation in sustainable design, while addressing other community needs such as energy generation. In order to partially offset the cost of the forest treatment processes which are to occur every 15 years (in any given area), the use of onsite bioenergy generation is proposed under three models; operating scenarios are illustrated for two of them.
The first aspect of this model was an evaluation of fuel treatment costs in threatened communities. Costs were determined to vary from a low of $130 per hectare for prescribed fire alone, to nearly $3,000 per hectare with a combination of prescribed fire and mechanical treatment. Although the cost of mechanical treatment was significantly higher, so are the secondary use options, and hence the potential for additional revenue. One commonly associated issue with mechanical treatment is the cost of transporting removed biomass to be processed offsite—something unfeasible for very remote areas. Because the proposed model makes use of biomass onsite, these costs are eliminated. Biomass that was required to meet energy needs under three energy generating system types, were based on estimates of total annual energy use within a given community. The fuels treatment plan was adjusted accordingly to produce a sufficient amount of biomass for the bioenergy systems; the preferred 15–20 year cycles (estimated time before fuel loading becomes hazardous again) was taken into account and the threat of wildfires was greatly reduced under the new management plan.
The three proposed energy generating systems all fall under the category of combined heat and power (CHP) systems, and are best suited for small scale operations; they are therefore of the more appropriate technologies for these remote communities (most often removed from the power grid to begin with). They are the small-scale CHP steam Rankine system, the organic Rankine cycle (ORC), and the entropic cycle. The small-scale steam Rankine system produces high pressure steam for electricity generation through a direct-fired biomass conversion system that uses a boiler. This system however has the highest capital cost and requires specialized labor. The ORC system, of which there is a proven model commercially available in Europe, has a lower environmental impact and a higher operating efficiency with a 10% (electrical) energy conversion rate. However, it uses a variety of working fluids as alternatives to water, many of which are very volatile. The final approach evaluated, and found to be most suitable, was the entropic cycle. This system uses a process combination of the ORC system and small scale Rankine system to have an overall conversion efficiency of 68% with 12% representing the electrical conversion portion. The entropic cycle is the safest option, does not require specialized labor, and is a closed loop system so it does not require external cooling components and is therefore smaller in size.
Yablecki et al. chose a base case community of 100 residents expending an estimated 240kW (from three small diesel generators) for the modeling exercise; they used data from small communities in British Columbia as reference. They ran two scenarios with the selected three models. The first scenario utilized the CHP systems at 75–100% operating capacity year-round, while using some energy derived from diesel generators to offset a small portion of unmet energy needs in peak times (i.e. winter). The second scenario utilized only biomass; therefore the biomass required as well as the radius of fuel treatment needed, was greater. Between all three CHP energy systems, the entropic system proved to have the lowest capital investment, the highest return, and the lowest biomass input requirements. It therefore had the lowest need for labor intensive treatment processes and the associated costs as well.
To evaluate the GHG emission reductions as a consequence of this community based CHP bioenergy production and forest management model, the authors replaced gasoline fueled vehicles with electrical plug-in hybrid vehicles. This new fleet of vehicles could derive all their power from the CHP system(s) while only minimally expanding the community bioenergy production model, simultaneously reducing the communities GHG emissions and their dependency on imported fuels. Finally, Yablecki et al. formulated a loose revenue model largely based on overall long term savings while highlighting the revenue streams under the two scenarios. The payback periods under the Entropic and ORC systems were 18 and 24 years, respectively. Considered for example, were the fuels treatment costs per hectare (an average of $1389), and a fuel consumption of 4.8 L per 100km for the hybrid vehicles (PHEV60).
Though the authors cautioned against the variability possible when applying this model to different areas on different scales, they contend that it is a valuable comprehensive community-based solution that goes beyond just mitigating the often devastating effects of wildfires within the WUI in the US and Canada. Yablecki et al. suggest that this model revitalizes communities and addresses a host of issues from public safety, preventative forest fire mitigation practices in remote areas, and maintaining forest health, while reducing GHG emissions and dependence on imported fuels. Overall, this model, suited for small communities, is a sustainability and bioenergy model that uses mechanical forest treatment as its primary support and supply mechanism to provide a wide range of community benefits.