Case studies
On this page you will find a number of sawmill case studies under the following headings:
Wood-fired boilers promise big savings for dairy factory
12 November 2007
The rising cost of natural gas prompted
Tatua Co-operative Dairy Factory near Hamilton to look at alternative
energy sources to run its boilers.
Wood-fired boilers are common in sawmills and wood processing plants, but are yet to be used in a New Zealand dairy factory.
Tatua’s site engineer Jack van Lankveld says they were motivated by
a desire to be more self-sufficient and environmentally friendly.
“If the [gas] supply went down we would have to stop operating.
There’s also the whole carbon issue to think about – this is something
that is becoming increasingly important.”
The company commissioned a feasibility study that found converting
to wood-fired boilers could cut its energy costs by up to $835,000 a
year. The cost of buying and installing the new boilers would be paid
back in five to six years.
The feasibility study looked at a range of issues, including how
much steam the factory uses, how much the demand fluctuates, and how
wood waste could be delivered and stored.
Before proceeding with the conversion to wood-fired boilers the
Tatua dairy factory must first find a long-term supply of reasonably
priced wood waste.
Download the full case study [PDF 98 kB]
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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
Mighty River Landfill Electricity Generation
Mighty River power generates electricity at three landfill sites,
two in Auckland (Greenmount and Rosedale), and one near Wellington
(Silverstream). Landfills produce gas which typically consists of 55%
methane and 35% carbon dioxide, with some nitrogen and other trace
gases. The methane gas produced by these landfills is combusted in
turbo-charged gas engines to produce electricity. Mighty River has
produced 626 million kWh of electricity for the year, ending June 2004.
Methane
gas is a significant contributor to the greenhouse effect and effective
destruction of methane gas to generate electricity helps to reduce the
country’s overall greenhouse gas emissions.
The following link describes the generation capability at the three landfill sites.
Mighty River Landfill Electricity Generation[PDF 164kb]
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Sawmills produce a wide variety of sawmill wood and wood residue.
These residues are a valuable energy resource for biomass energy
palnts. However, the residues produced are often difficult to handle
due to their variable sizes and different moisture contents. Creating
automated systems to handle these waste streams and act as fuel feeds
requires specialized knowledge and is best tackled on a case by case
basis.
Brightwater Engineers
have been involved in many New Zealand based projects designing,
building, installing and commissioning integrated fuel handling
systems. Three example case studies on fuel handling systems are
outlined below:
Brightwater Hog Feed System
The Brightwater Hog Feed System was initially designed for Blue
Mountain Lumber sawmill in Southland. The sawmill generates significant
quantities of green sawdust, wood shavings, and lumber off-cuts which
is utilised for a 10MWth steam and electricity co-generation plant.
The
site requirement was for a system capable of handling the total range
of wood residues and converting them into boiler fuel by passing them
through a size-reducing hogger. It was also a requirement to be able to
feed these residues into the hogger as either individual streams or as
a mixture of different residue types.
Brightwater Engineers designed
their Hog Feed unit to handle all material types and to provide a fully
automated reception and discharge bunker mechanism.
Follow the following links to read more:
BANZ project report [PDF 123kb]
Brightwater Engineers project report [PDF 100kb]
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Tachikawa Wood-Waste Handling System
Tachikawa Forest Products has
a sawmill located in Rotorua. In 1997 Tachikawa installed a 8 MWth
boiler to be fired on wood residues. The majority of the fuel required
by the boiler is produced on-site as a by-product of the sawmill
process. Additional wood residue required is trucked to the site from
other local wood processors.
Brightwater Engineers designed, built, installed and commissioned an integrated fuel handling system to meet Tachikawa’s needs
The following links describe the fuel handling system at Tachikawa in more detail:
BANZ project report [PDF 106kb]
Brightwater Engineers project report [html]
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Pan Pac Forest Products Fuel Handling System
Pan Pac Forest Products,
near Napier, have an integrated sawmill and pulp mill. Pan Pac required
a fuel handling and management system to store and deliver fuel to a 36
MWth boiler.
The fuel comprises of course green wood residue and dry
shavings. The fuels require storing separately but delivering to the
boiler in a blended and metered condition according to demand.
Brightwater
Engineers designed and built equipment to store and reclaim course wood
residue as the primary fuel for the boiler, a shavings handling and
storage system to store and discharge shavings to blend with the
primary fuel.
The following link describes the fuel handling system at Pan Pac in more detail:
BANZ project report [PDF 89kb]
Brightwater Engineers project report [html]
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Hoggers Opening Up New Energy Options In Forestry
Forestry
generates huge quantities of wood residues. Those residues could be a
valuable new source of carbon-neutral energy for the industry and New
Zealand.
In practice however, using wood residues is
difficult in some sectors of the industry, particularly in forests
after cutting. Here, the process can end up costing more than using
coal.
Machines called ‘hoggers’ have been developed which are specifically designed for processing wood residue from forests.
As
part of a new initiative coordinated by the Energy Efficiency and
Conservation Authority (EECA), researchers have studied the economics
of these machines in New Zealand conditions.
The
bottom line is – today’s hoggers are making wood residue a practical
and economic energy option in more situations than ever before...more
Where wood processing residues are insufficient to meet the fuel
demand for a biomass fuelled boiler then alternative fuel supplies need
to be considered. One fuel to consider is forest residues at landings
and skid sites within the forests. Providing factors affecting supply
are appropriately evaluated then these forest residues can be a cost
effective fuel.
The following link describes a hypothetical assessment of the
potential supply and cost of forest residues to a bioenergy plant. Wood Processing Residues As Fuel [PDF 112kb]
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Wood boiler fuel - Payment by energy versus weight – Case study
This study determines the effects of moving from a payment system based on weight to a payment system based on energy‑content at a large industrial site, using woody biomass as a fuel source. The benefit of paying by energy content would be that the purchaser could predict how much fuel he would need to buy to meet a specific energy demand. An energy-based payment system could also lead to delivery of better quality fuel (i.e. drier and cleaner), thus helping to overcome one of the barriers to increased use of wood residues as a fuel. Paying by energy content avoids the issue of over- or under-payment, which can happen with weight-based payment systems... read case study.
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Woody biomass for boiler fuel -
Guidelines for payment by energy content
A
payment system based on energy content is one method of ensuring a high value
fuel, which is paid for in a manner fair to both buyer and seller. The higher
the quality of the fuel, the higher the energy content, the higher the value to
both seller and purchaser. This report makes practical recommendations on how
to move from a weight-only system to a simple weight-by-moisture content system... read case study.
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Forest residue recovery study - Hogging direct to truck versus
hogging to ground - fibre loss and cost issues
The
Wood Energy Programme Engineering Solutions Phase I study identified a number
of potential opportunities to improve the efficiency of forest residue derived
fuel delivery. One of these was to reduce fibre loss during hogging and
loading.
Current
practice is for the hogger out-feed to discharge hogged material directly onto
the ground, and trucks are loaded from a stockpile of hogged material with a
front-end loader. The goal of this study was to determine the fibre loss
associated with hogging onto the ground and compare this with hogging directly
into a truck. Fibre loss in the order of 4% was found in the hog-to-ground
system.
The
potential differences in trucking costs were also examined as hogging into a
truck entails increased loading time, and the extra cost of the truck and
driver may or may not be offset by the reduced fibre loss... read case study.
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Turning forestry waste into renewable energy
18 July, 2007
In New Zealand,
residue from forest harvesting is usually left to decompose. Forestry
practices and environmental conditions in New Zealand have made it
difficult to efficiently extract and use forestry residue. However
machinery has been developed that allows processing of forest residue
on-site, in local conditions. These machines, called hoggers, produce
processed wood used to fire boilers.
In the central North Island, forest
residue is now being collected from several forests, processed on-site
into boiler fuel by hoggers and delivered to pulp mills. The practice
is expected to become more widespread as fossil fuels and electricity
become more expensive.
This case study reviews three hoggers’ performances and identifies the key drivers of efficiency.
Read the full case study (PDF)
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CHH – Kinleith Mill, Tokoroa, New Zealand (October 2005)
Kinleith is an integrated kraft mill that converts radiata pine into
kraft pulp and a range of packaging papers. Kinleith’s five-year plan
for efficiency cut energy consumption by 31% per tonne of product.
Despite production increasing by 25%, carbon dioxide emissions remain
stable.
Key factors in Kinleith’s success in energy management include:
- Appointing a specific person to champion energy management
- Setting key performance indicators, such as energy consumed per tonne of product
- Seeking expert advice, nationally and internationally
- Formalising the energy efficiency initiative through the Value Creation Project
- Seeking creative thinking from staff
- Thinking about alternatives to buying-in electricity and gas
The following link describes the steps taken by CHH Kinleith to increase energy efficiency.
Full report [PDF 808kb]
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Juken Nissho – Waiarapa Mill, Masterton, New Zealand (April 2004)
The Waiarapa Mill manufactures laminated veneer lumber (LVL) for
export to Japan. The 29 MW boiler has been fitted with two PDL
UltraElite variable speed drives from Schneider Electric (NZ) Ltd. The
larger drive was fitted to remedy poor performance during periods of
low load, and the smaller drive was installed to allow easy adjustment
of the air being forced into the boiler.
The efficiency of the
boiler has been improved at low demand times. When the boiler is
running at low levels, it no longer emits the smoke that was a sign of
running inefficiently.
Full report [PDF 140kb].
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Sawmills find renewable energy - and cost savings - in wood waste
6 August, 2007
A North Island sawmilling company recently
switched from electricity to wood residue for its boiler fuel and has
found it to be a very cost effective energy option.
The company previously used electrically heated kilns to dry timber,
but it recently phased out the electrical system in favour of kilns
heated by a central boiler that burns wood shavings from the milling
process.
The company produces 39% of the shavings required to run the boiler
and buys the rest from other suppliers. It is considering installing a
multi-fuel boiler in the future, which would burn other by-products
such as sawdust and bark, reducing the need to buy fuel from elsewhere.
Wood residue now accounts for 84% of energy usage at the company’s
mills, with electricity providing the rest. However, the cost of wood
residue represents only 10% of the total energy bill, while electricity
costs represent 90%.
The switch to this renewable energy resource has the potential to save the company over $300,000 a year in energy costs.
Read the full case study (PDF 454KB)
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Sawmill considers energy centre options
6 August, 2007
TDC Sawmill is looking at ways to generate steam energy for a proposed energy centre at its fortress mill in Whangarei.
The Mill produces greenwood timber but TDC plans to install driers
so the mill can increase its output by also turning out dried and
planed timber. The new driers would require an energy centre.
A feasibility study by Process Developments Limited identified five
options for the energy centre, all involving wood-fired boilers. Some
options also included cogeneration or gas.
As well as capital and running costs, the study covers a range of
engineering issues and recommends preferred technologies for the site.
The feasibility study will help TDC to identify the most suitable option.
Read the full case study (PDF 98KB)
Forest Research (now Scion) produced this report providing an
overview of energy use within the NZ wood processing sector in 2002.
The wood processing sector supplied over 50% of its own energy in the
form of biomass (wood process residues and black liquor). Electricity
represented 18%, natural gas represented 17% and geothermal steam
represented almost 10% of the total energy use.
The 2002 survey indicates that the total energy use by the wood
processing sector had increased by over 40% from the previous 5 years.
This increase could be attributed to marked increases in production
with a 30% increase in sawmill production and a 40% increase in panel
production, and a significant expansion of the use of wood processing
residues for energy production.
Full report [PDF 659kb].
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Sawmill leaves gas bill for dust
18 July, 2007
Kiwi Lumber’s sawmill at Dannevirke has cut its gas bill by turning its leftovers – sawdust and wood shavings – into energy.
The sawmill had been using a gas fuelled boiler for drying timber,
but the rising cost of gas led it to look for a cost effective and
sustainable alternative.
Using wood residue instead of gas to fire the boiler saves the
sawmill 19GWh in gas a year. Other benefits include fewer loads to the
landfill and a saving of 2,280 litres of water a day.
A feasibility study put the sawmill’s waste by-product in a new
light. It found that 96% of the sawmill’s energy demand could be met by
powering the sawmill’s kilns with water heated by burning sawdust and
wood shavings.
Management compared the cost of installing a wood residue fired
boiler system with the savings from not using gas. The figures looked
good.
Having made the switch, wood residue now provides 89% of the sawmill’s energy needs, with electricity covering the rest.
Read the full case study (PDF)
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Sawmill energy audits
EECA has published a summary of audits in the New Zealand sawmill
industry. These audits assess energy use by the sawmilling industry and
identify potential for energy savings.
The major operations consuming electricity on a sawmill site are
debarking, sawing, kiln-drying, treating and planning. However each
site varies as to which operations are occurring.
Burning wood waste is the major source of energy used at the
sawmills, primarily in kiln drying. Bioenergy comprises 57% of the
total energy used and 4% of the total energy costs.
Fossil fuels such as LPG, coal, diesel and recycled fuel oil
comprise 32% of energy use and 33.4% of energy costs. These fuels are
typically used for kilns drying and for drying wood waste.
Electricity comprises 11% of energy use but 62.5%of energy costs.
Full report [PDF 489kb].
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