Public health professionals who work in cold climates, rural or low-income communities know that wood heat is central to the home energy equation. There are cleaner, greener alternatives, but none match the trifecta that wood heat offers: affordability, reliability and comfort. But those in public and environmental health also know that combustion of biomass produces a complex suite of contaminants. In the literature, these contaminants are strongly associated with upper and lower respiratory diseases (infectious and chronic in nature), and adverse cardiovascular events, such as premature stroke and heart attack. Less well understood, but possibly more insidious is the carcinogenic, mutagenic and immune-suppression effects of woodsmoke, for which the research shows a strong correlation. In short, wood heat poses a complex public health threat, meaning we must approach the challenge with respect, innovation and patience.
As practitioners, our goal is to find interventions that are evidence-based, low-cost and sustainable. These are hard to come by. The default intervention, for the last two decades, has been to replace an aging woodstove with a new, certified stove. Change-out programs have an evidence-base, but are expensive. And research has shown that emissions reductions are not necessarily sustained, as the device ages, or is inadequately maintained. Another device-based intervention is fuel conversion. But while natural gas and propane contribute to the collective good (improved air quality, fewer public health and climate change impacts), the ledger for households doesn’t balance: the up-front investment is high, many parts of Alaska and the rural west are outside service areas, and fluctuations in monthly heating bills are a deterrent.
These realities, along with the long cultural history of fire use, point us towards one of the few variables we can reasonably manage: the fuel itself – more accurately – the moisture content of the firewood.
Wet wood, it turns out, is a pivotal factor in combustion chemistry, and both the toxicity and volume of gaseous and particulate emissions are tied to moisture content (Bølling, 2009, Hall and DeAngelis, 1980; Burnet et al., 1986; McDonald et al., 2000). But the reality for consumers is that wet wood is also “a waste”. Green firewood (60-70% moisture content) produces about 5,000 BTUs of energy per pound, versus an average of 7,700 BTUs produced by properly seasoned firewood (15-20% moisture content). And when the effective available heat is low, more wood (meaning more money) will be needed to produce the same amount of heat. Most families who rely on wood heat are well aware that cured wood produces a hotter, longer-burning, and cleaner fire. So from a public health standpoint, awareness is not our principal concern. Rather, it is the barriers we need to address. These barriers include lack of access to a consistent firewood supply, inadequate places to store, dry and cure wood, and inefficient fire-building practices, such as the use of household waste.
These barriers are not unique to Alaska, but are seen throughout the west, in many of the tribal communities that Tribal Healthy Homes Northwest works with. Through our field research and demonstration projects, we collaborate with dozens of tribes to address woodsmoke, but only recently did we learn about a new, innovative approach, called “Wood Banking”. The concept is simple: you deposit your wet wood, and you withdraw the same quantity of dry wood. The logistics may not be so simple. In our initial research, we’ve learned that you need an accessible, secure location. You need to build a structure large enough to house and protect a large volume of wood. You may not need a full-time operator, but you need someone on-site at least weekly. And you need the initial investment of time or money, in order to either purchase or spend a year curing a large volume of wood.
Still, the potential benefits are intriguing. A cooperative could be formed, for example, in which a small annual fee enables a household to participate (their investment offset by having dry, more efficient wood, and having to purchase fewer cords each season). The fees would help pay for an on-site operator. This operator could be anyone, but in our experience, there are many independent firewood suppliers with both a truck and a desire for added income. That person could be paid, for example, to operate the wood bank each Saturday from 8am – 12pm, using a forklift to help people load and unload their wood. During the week, for those who need help, the operator would pick up a load of wet wood from a person’s home, make the exchange, and return with the dried wood.
Some climates and communities will not be a fit for this approach. In much of the biomass-rich western US, however, and in some regions of Alaska, the model may prove viable. Public policies are guiding us towards more intensive interventions and the use of green heat technologies, but until these are adoptable on a larger scale, this approach should be considered. For a low-technology, low-cost intervention, the potential improvements to ambient and indoor air quality could be significant.
Published by: Erika Whittaker in Updates