Elevator version:
The trees and lakes in Muskoka, and many other Canadian Shield regions, are suffering because they don’t have enough calcium.
Wood ash is an excellent source of calcium, but much of the ash from wood stoves is wasted. Some goes to landfills; some is dumped in backyard ash piles. Many tons of firewood from central Ontario forests are trucked to wood stoves in southern Ontario, where forests and waterways do not need more calcium. We want to see this tremendous resource put to good use with a wood ash recycling program that will gather wood ash from local wood stoves as well as from wood stoves in southern Ontario and spread it in forests in Muskoka and beyond where it is of greatest benefit.
Preliminary studies by Friends of the Muskoka Watershed and other groups have shown that the science is sound, and there is enough ash available to make a significant difference. The next steps are:
- Determine exactly how much ash should be spread per hectare of woodland
- Develop an ideal way of spreading it
- Start to collect ash from homeowners through a recycling program
Ash Muskoka is a three-year project to answer those questions. Volunteers and staff have been distributing ash cans to local residents and are receiving the ash at local landfills on Ash Drive days. Scientists from several universities are setting up test plots in maple sugar bushes to spread ash and measure the results.
By the end of year three, we aim to have collected 100 tonnes of wood ash. We also intend to have all the information we need to set up a full-scale wood ash recycling program.
We are doing this with support from several essential groups, including the District Municipality of Muskoka and the Ontario Maple Syrup Producers, and with financial support from the Ontario Trillium Foundation.
Enhanced factoids
How much wood ash is needed?
In the first two years of the project, we will need 100 to 200 residents to donate five to ten tonnes of ash. By year three, we will need at least 1,000 residents involved, donating 50 to 120 tonnes of ash. We believe this to be about half of the wood ash generated each year in Muskoka. The goal is to be able to spread around four tonnes of ash per hectare of woodland.
How much calcium does wood ash contain?
The amount of calcium in wood ash depends on the tree species burned, the presence of tree bark, andสthe chemistry of the soil where the trees grew. Calcium levels in wood ash can vary between 15% to 50% of total ash weight. On average, wood ash generated from hardwood tree species in Muskoka contains 29% calcium by weight.
Is this just about calcium?
No. Wood ash has several elements that are vital to tree growth, including potassium, magnesium, and phosphorus. Other elements present in wood ash are sodium, iron, manganese, and sulphur. There is little to no nitrogen present in wood ash as it is lost during combustion. Calcium is, however, the most significant element in wood ash because it is the element that is limiting tree growth and health.
What about contaminants?
There is no evidence yet that any contaminants in wood ash are present at levels damaging to the forest. Samples of contributed wood ash were tested for 11 trace metals – arsenic, cadmium, chromium, cobalt, copper, mercury, molybdenum, nickel, lead, selenium, and zinc. However, the metal levels in this non-industrial wood ash (NIWA) fall well below the targets for restricted use. Should metal levels in wood ash be above these targets, it would have to be disposed as a hazardous waste. All current evidence indicates NIWA won’t face this restriction.
I just dump my wood ash in the backyard. Is that OK?
Yes and no. The potassium in wood ash is very water soluble. Potassium is an essential nutrient for growth and reproduction in plants and for muscle strength, water balance and the nervous system in mammals like you and me. But too much of it is not good. Dumping your wood ash in one area might lead to localized potassium toxicity. Putting ash in a thick pile can also make it more difficult for the calcium to leach into the soil, where it is needed. Selectively adding wood ash to the garden or around the drip line of maple trees in measured amounts can be beneficial, however not all areas within Muskoka require the same amounts of added calcium. Thus ASHMuskoka’s focus is to deploy on a large scale where it is most needed.
How will wood ash from southern Ontario be brought up here?
Municipalities in Muskoka currently send hundreds of truckloads of waste to landfills in the south. Those trucks return empty. They could be used to carry wood ash from southern Ontario landfills, helping to reduce the landfill burden there and helping to improve forest and watershed health here.
