Energy Efficiency in the Production of Wood Shavings
The Office of Energy Efficiency of Natural Resources Canada (NRCan) offers a financial incentive through its Canadian Industry Program for Energy Conservation to help businesses find ways to increase their energy efficiency, improve their production processes and reduce their costs. This incentive covers up to 50 percent of the cost of hiring a professional energy auditor, to a maximum of $5,000.
In 2004, with help from the Industrial Energy Audit Incentive, Rip-O-Bec inc., a manufacturer of wood shavings for animal bedding, had an energy audit done of its plant in Saint-Apollinaire, Quebec. The energy efficiency measures proposed by the audit included reducing the plant's use of propane by replacing the propane furnace connected to the shavings dryer with a sawdust burner, recovering the heat produced by the plant's electricity generators to heat adjacent offices, and replacing diesel generators with ones that run on natural gas.
By switching to a sawdust burner, the plant was able to discontinue its use of propane in the drying process and achieve annual savings in excess of $160,000. Since the installation of the new burner in December 2004, the plant has not only reduced its energy costs by more than $10,000 per month, it has also more than doubled its production compared with the same period in the previous year.
- Propane use reduced by more than 95 percent
- Energy savings exceeded $160,000 annually
- Production increased by over 100 percent
- Greenhouse gas emissions (GHG) reduced by more than 700 tonnes of CO2e annually
Rip-O-Bec inc. specializes in making wood shavings from virgin fir and pine for use as animal bedding. The company manufactures three sizes of dry shavings:
- large, for the comfort and hygiene of racehorses
- medium, primarily for horses, but also suitable for other livestock
- small, for cattle and hogs, providing a high level of moisture absorption
The company's plant in Saint-Apollinaire has facilities for debarking and cutting logs into wood chips and for screening, drying, bagging and storing the shavings. Once the logs have been processed, the bark and other larger pieces of wood are separated from the shavings by screening. The shavings are then dried in a constant-temperature kiln. The end product – the dried shavings – is sorted by size, using mesh screens of different diameters, and then packed in waterproof bags and sealed against moisture. The final screening process also removes fine sawdust particles. The wood residue recovered in this process is used to fuel the burner.
Approximately 60 percent of the wood chips used for producing the shavings are made from logs on-site. The remaining 40 percent is purchased from outside suppliers and then processed at the plant.
The drying process used to require propane; and in 2003-2004, more than 500,000 litres of propane were used, at a cost of over $160,000. In the area where the plant is located, Hydro-Québec does not provide electricity at the voltage level required for the production equipment. Therefore, the plant uses diesel generators to produce the electricity for production (there is no electric heating). During the same period, the company used more than 200,000 litres of diesel, at a cost of more than $100,000.
SPAP Énergie, a consulting engineering firm specializing in energy audits, conducted the audit of the Saint-Apollinaire plant. Rip-O-Bec inc. received financial support from the Office of Energy Efficiency equal to 20 percent of the professional fees for the study. The audit covered all the production equipment but focused mainly on finding ways to reduce the plant's propane consumption. The plant's electrical equipment is relatively new and efficient, and the audit did not yield any potential energy efficiency measures with an attractive payback period. The energy efficiency measures recommended by the audit were as follows:
- Replace the propane burner connected to the drying kiln with a sawdust burner that is fuelled by wood residue produced at the plant, with a payback period of 0.6 years
- Recover the heat generated by the diesel generators and use it to heat adjacent offices, with a payback period of 4.3 years
- Replace the diesel generators with ones that run on natural gas, with a payback period of 8 years
Plant management selected energy efficiency measures based on their payback period. Switching to a sawdust burner was deemed the most profitable measure.
The shavings produced by Rip-O-Bec inc. are kiln-dried for maximum moisture absorption to ensure animal comfort and hygiene. The burner heats the air to just over 148.9°C (300°F), and then the air is blown into the kiln, which rotates to tumble the wood shavings and produce uniform dryness. An evaluation of the amount of sawdust generated at the plant showed that there was enough residue to fuel a burner with a greater heating capacity than the existing one. In fact, burning the residue produced on-site would produce enough energy to dry a significantly larger volume of shavings than was currently the case. This represented an opportunity for the plant to increase its production considerably while cutting the cost of fuel required for the drying process.
Energy Unlimited Inc. manufactured the sawdust burner now connected to the kiln. The insulation, fans, and burner controls and sensors were included in the purchase price. The manufacturer also installed the burner and helped to get it up and running. The installation work, which began in December 2004, took about four weeks and required shutting down production entirely.
The purchase price of the burner, some of the equipment required for its operation and the labour required for its installation totalled just over $150,000. Thanks to NRCan's Renewable Energy Deployment Initiative (REDI), which promotes the use of renewable energy systems for space and water heating and cooling, Rip-O-Bec inc. obtained a $40,000 subsidy to help offset these costs.
Note that, when calculating the payback period, Rip-O-Bec inc. factored in only the subsidy it received for offsetting the purchase and installation costs of the new burner. The calculations did not include the earnings lost because production had to be stopped to install the burner.
By implementing one of the measures identified in the energy audit, Rip-O-Bec inc. reduced its annual energy costs and increased its production significantly. Simply eliminating the use of more than 500,000 litres of propane annually for kiln drying saved about $160,000 a year and reduced the plant's greenhouse gas emissions by more than 700 tonnes of carbon dioxide equivalent (CO2e).
The high cost of propane for heating the drying kilns had been the main factor limiting the plant's production levels. By replacing propane with the wood residue generated on-site as the energy source for the kiln dryer, the plant was able to upgrade to a higher-capacity furnace and thereby increase the quantity of shavings that could be dried, while eliminating fuel costs. Within three months of installing the sawdust burner, the plant had more than doubled production and saved over $30,000 in fuel costs, compared with the same period in the previous year.
The decision to implement a recommendation from the energy audit has proven to be profitable for Rip-O-Bec inc., given that the proposed measure had a payback period of only 0.6 years and the sawdust burner has a service life of about 25 years. What is more, the plant may further increase its energy savings, as it is looking at recovering the heat generated by the diesel generators and using it to heat the adjacent offices.
629 Bourret Road
Saint-Apollinaire QC G0S 2E0
Web site: ripobec.com
107 quai Saint-André, Suite 303
Québec QC G1K 3Y3
Energy Unlimited Inc.
Web site: energyunlimited.com
Canadian Industry Program for Energy Conservation
Office of Energy Efficiency
Natural Resources Canada
Web site: oee.rncan.gc.ca/industrial/cipec.cfm
The digital mosaic of Canada that appears on the cover of this publication is produced by Natural Resources Canada (Canada Centre for Remote Sensing) and is a composite of individual satellite images. The colours reflect differences in the density of vegetation cover: bright green for dense vegetation in the humid southern regions; yellow for semi-arid and mountainous regions; brown for the far north where vegetation cover is very sparse; and white for the Arctic regions.
© Her Majesty the Queen in Right of Canada, 2007
Cat. No. M144-132/1-2006E
Aussi disponible en français sous le titre :
Étude de cas : Rip-O-Bec inc. – Efficacité énergétique dans la production de copeaux de bois