Waipa sawmill turns out timber – and electricity
18 July, 2007
The Waipa sawmill near Rotorua has been generating its own electricity for over 50 years, cutting its costs and returning power to the national grid.
A large sawmill produces a lot of sawdust, bark and off-cuts. At Waipa, these byproducts provide fuel for a ‘cogenerator’ that produces heat for timber processing, as well as extra electricity that is sold to TrustPower.
In a typical month, the sawmill spends about $40,000 on electricity but also generates and sells $20,000 worth – essentially halving its power bill.
Chief Financial Officer Paul Laing of Red Stag, the company that owns the sawmill, says the
electricity savings could be as much as $1 million a year.
While the cogeneration plant’s main purpose is to reduce the sawmill’s power bill, there are plans to enable it to sell 100% of the electricity generated on days when the sawmill is closed.
Download the full case study (PDF)
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Blue Mountain Lumber Energy Facility
18 July, 2007
Blue Mountain Lumber is a sawmill located in Southland, New Zealand. The sawmill was expanded in 2000 to enable the processing of approximately 160,000 tonnes sawlogs annually. Prior to
expansion the sawmill operated with several small wood residue fuelled boilers that were at the end of their economic life. The site was dumping significant quantities of woodwaste into a local landfill.
As part of the expansion an energy facility was built to provide improved steam quality and capacity for increased steam loads. The energy facility consists of a 10 MWth steam boiler fuelled with on-site wood residues and a 1.4MWe steam turbine generator to utilise any surplus steam for electricity generation.
The following link describes the energy facility, its operation, and the project parties involved.
Blue Mountain Lumber Energy Facility [PDF 159kb]
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Wood-fired gasifier under the spotlight
12th October,2008
Canterbury Clay Bricks (CCB) considered installing a wood-fired gasifier to heat their kilns and found that it didn’t stack up economically - but it could be an option in the future.
CCB manufactures clay bricks with a tunnel kiln fired with used oil and some diesel. The company is installing a second kiln and is looking at alternative, low-cost fuels to reduce their overall fuel bill. A wood-fired gasifier was one option investigated in a feasibility study by the Centre for Advanced Engineering New Zealand.
The study found that switching from gas to gasified wood isn’t currently economical, due to the low cost of it’s current used oil and the relatively high price of wood fuel used in the study.
The annual savings from switching to producer gas are about $75,000. Along with the start-up investment of $1.3 million, the study found that the payback period would be more than 15 years.
The study also considered whether carbon credits would make a gasifier more cost effective. Credits could help reduce the overall cost but the payback period would still be more than 8 years.
However a gasifier would increase health and safety and operational requirements and would also make the plant more flexible as it could run on either gas or liquid fuels. There would also be marketing opportunities from using a renewable fuel.
Read the full case study [PDF 91kb]
...topBioenergy Cogeneration Plant estimated to contribute $1 million annually to the bottom line
The bioenergy cogeneration plant at Red Stag Timber in Rotorua is turning 21 years old. It’s the most recent in a long line of cogeneration plants at the site dating back to 1939, and it’s one that the owner estimates contributes $1 million annually to the bottom line (before interest & depreciation). This case study tracks the plant through its conception, growth, and prospects in today’s volatile energy markets...more
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