Published Sep 15, 2021
By its very nature, our art form is not the greenest of artistic endeavors, but happily, many ceramic artists and organizations are taking it upon themselves to try to lessen their impact on the environment. One such organization was actually built on sustainability: the Energy Xchange in North Carolina.
In today's post, an excerpt from Sustainable Ceramics, we'll learn about two Energy Xchange kiln designs that make smart use of various forms of waste. - Jennifer Poellot Harnetty, editor
The EnergyXchange is nestled in the Black Mountains of western North Carolina, and the area is rich in cultural, natural, and historic assets including the legendary Penland School of Craft. When the landfill that served the residents of the area was closed in 1994, extensive research and discussion took place to find a use for the potential energy. Landfill gas production (approximately 40 to 60% methane) results from chemical reactions and microbes acting upon the waste to break down in the landfill.
EnergyXchange has become one of the US's model energy recovery projects and is used regionally, nationally and internationally as an example of successful small landfill gas projects. Since 2000 the EnergyXchange has provided rental studio space to over 20 resident artists in a Glass studio and a Clay studio, and has become known for the goal of turning unused landfill waste into fuel for these craft studios. For the ceramic artists most of the attention has been focused on the gas-fired ceramic kiln (read this article to learn how to efficiently fire a gas kiln!) which is fueled with the methane gas captured from the landfill.
The Methane Kiln
The landfill gas (LFG) used throughout the campus is extracted through several wells drilled into the sealed-over landfill site. The pipelines run from the collection wells to a central manifold and blower station. The blower pulls the gas out of the landfill, and pushes it through the pipeline towards the sites on campus where it is used.
The original ceramic kiln at the site is still in operation over 10 years after it was built. In most aspects it resembles other 'typical' gas-fired reduction kilns in the area. It has 67 cubic feet (1.9 cubic meters) of volume, with around 27 cubic feet (0.76 cubic meters) of stacking space. The working floor of the kiln is built out of hard firebrick, while the rest is composed entirely of insulating firebrick nine inches (23 cm) thick (firebrick is commonly used to describe a brick capable of repeated firing to high temperatures and used in kiln construction.
Lightweight insulating brick are typically used for wall and arch construction). After initial firings, a layer of fiber blanket and 'mud' coating was added as extra insulation. The kiln's original chimney was six feet of brick topped off by another eight feet of metal pipe, which was recently replaced with brick entirely. The kiln is powered by forced air burners, purchased from Ward Burners, and designed to operate on the low-pressure and low-heat content gas. This situation required that the orifice commonly used to restrict high-pressure gas be left out of the burners. As a result the burners have no orifice, and instead the half-inch (1.3 cm) pipe is left open to deliver the landfill gas at as high a volume as possible.
Over the years it has been used to fire everything from bisque ware to stoneware, and under current conditions the kiln can be fired to cone 10 in approximately 14-18 hours. As an estimate, a kiln of similar size fired with propane (LPG) might require around 45-50 gallons (170-190 liters) to reach cone 10. This represents not only significant financial savings for a potter, but also a sizable amount of landfill gas that would otherwise escape into the atmosphere as an unused resource.
In 2010 a wood-fired soda kiln was added at the EnergyXchange, designed by Mark Peters to take advantage of a supply of discarded wooden pallets. The Pallet Kiln represents not only a second innovative use of local waste material, but also provides a model for others on a scale smaller than that required for landfill methane gas.
The Pallet Kiln is built of a hard brick interior and insulated brick exterior, with a firebox and stokehole large enough to accommodate full pallets. The kiln is 167 cubic feet of total volume (38 cubic feet of stacking space) and consumes approximately 100-120 pallets when fired to cone 10.
The kiln's oversized firebox and abundant inlet flues make it possible to stoke the kiln repeatedly with a full pallet (approximately 40 x 40 in (102 x 102 cm)) nails and all. Initial concerns of nails suspended on the sides of pots proved unnecessary, thanks perhaps to the depth and width of the internal firebox.
Over the course of the first year the kiln was fired to cone 10 six times, typically lasting around 18-20 hours and consuming around 120 pallets each time.
To learn more about Joy Tanner and see more images of her work, please visit http://joytannerpottery.com/.
To learn more about William Baker and see more images of his work, please visit http://williambakerpottery.com/.
**First published in 2013