Biomass case study

Case Study

Biomass Boiler Installation at Newbridge Sawmill, BSW Timber

IntroductionBSW Timber is the largest sawmilling business in Great Britain, with a 35% market share of home supply of soft woods in the UK. The firm employs 750 people across the UK and Latvia and has a turnover of over £130 million. BSW produces over a million cubic metres of sawn timber per year in the form of hundreds of different timber products from decking to packaging; BSW has eight distribution sites.

BSW Timber’s Newbridge Sawmill is located near the spa town of Llandrindod Wells and has been operating on the site since 1980. In recent years, the sawmill has been producing approximately 108,000m3 of timber product per year, the majority of which has been kiln dried via six oil-fired kilns, normally operating for around 70 hours per week, rising to 24/7 operation during periods of peak production. The kilning operations represent almost all of the 6,025MWh heat demand at the site.

Project HighlightsThe installation of a 6MW biomass heating system at Newbridge Sawmill, fuelled by their onsite wood waste, has enabled the annual kilning capacity to increase by over 100%, whilst reducing the site’s energy costs, this will result in carbon savings of 2,400 tonnes per year.

Aerial View of BSW’s Newbridge Sawmill

Project AimsBSW wished to explore the possibility of replacing the existing oil consumption with their low value co-products generated on site to fuel the kilns. The sawmill produced approximately 26,250 tonnes of wood co-products per year with a moisture content of up to 55%. By utilising some of this biomass energy, BSW’s main aims were to reduce fossil fuel costs and haulage costs for the removal of the wood co-products from the site, generate an income from the Renewable Heat Incentive and reduce carbon emissions.

BSW also wanted to increase the use of the existing kilns, resulting in an increased heat demand of 8,830MWh per year; this is now supplied by the biomass system and has resulted in a reduction in operating costs and environmental impact.

Biomass case study

Boiler House and Fuel Store under Construction2 x 25,000 litre Thermal Stores in Position

The 6MW plant at our Newbridge on Wye, Mid Wales facility was commissioned during June 2011. The project was on schedule, to budget and is exceeding our performance expectations.

Dave Burd Mill Manager of BSW Newbridge

• Assistance with Carbon Trust loan application to part-finance the capital costs of the installation.

• Planning support.

• Provision of technical support throughout construction, evaluation and handover.

With this technical assistance and expertise, the project evolved from a replacement of the existing oil fired plant with biomass, and gave BSW with the confidence to invest £1.6m in the project enabling a business development via an increase in kilning operations. As confidence continued to grow, BSW subsequently installed similar biomass heating plants at a further two sites, with a total thermal capacity of 20MW.

Construction at Newbridge began in January 2011, commissioning and handover of the plant was completed in June 2011.

the proposed solution was presented, including boiler house layout and integration with the existing kilns district heating main around the site.

The feasibility process provided BSW with sufficient information to make an informed decision to invest further resources to develop the project. In order to ensure that the installation was delivered at lowest optimal cost and at very high levels of technical performance, the project was progressed to the next phase of development through the Carbon Trust’s Biomass Heat Accelerator, in which the technical consultants, Sustainable Energy Ltd, covered the following activities:

• Detailed system design.

• Technical specification of all plant items.

• Assistance with tendering for boiler supplier and main contractors.

Project DevelopmentHaving been identified by the Carbon Trust’s Biomass Heat Accelerator as a key site to take advantage of biomass heating, BSW was provided with part funding, by the Carbon Trust, towards the technical consultancy fees. Sustainable Energy Ltd were selected to oversee the project from concept to project management and commissioning. As the first step Sustainable Energy conducted a feasibility study to assess the viability of a number of different options in terms of plant location, specification, size and cost. After much consideration and discussion between BSW and Sustainable Energy Ltd, it was concluded that the optimum solution for the site would be 2 X 3MW biomass Medium Temperature Hot Water boilers to provide 100% of both the existing heat demand and increased heat demand. An outline design of

The boiler house and thermal storage is shown below and right.

Projected Biomass SavingsThe cost of processing the wood fuel at the site is £23/tonne; the wood fuel at Newbridge has a calorific value of approximately 2,000kWh/tonne. With an average biomass boiler efficiency of 80%, the delivered heat cost via biomass is now 1.4p/kWh. The biomass plant will generate over 8,830MWh of renewable heat per year. In addition to the savings that this low cost heat offers over a fossil fuel alternative, the annual income from the Renewable Heat Incentive will be £88,300 per year, based on the Large Biomass tariff guidelines – this is calculated as shown below:

Biomass case study

Completed Boiler House – Thermal Stores

Completed Boiler House – Boilers and Boiler Pump Sets

Technology (kWh) Tariff (p/kWh)

RHI Value per year

Large scale biomass boiler

8,829,800 1 £88,298

Technical DetailsThe biomass boiler solution comprises of 2x3MW moving grate boilers with 50,000 litre thermal storage, sized to maximise the operational efficiency of the biomass system. The thermal store can be charged up in periods of lower site demand and then used to supply low and peak heat demands that are outside of the operational range of the boiler, in order to ‘even out’ the demand on the biomass boiler.

The load profile from the kilns is different to a conventional heating system, but the benefit of the thermal store has been seen. The immediate availability of Medium Temperature Hot Water from the thermal store (responding more quickly than the previous oil fired plant) has enabled the kilns to reach operating temperatures more quickly. This has reduced the potential batch

time on the kilns, enabling a greater throughput.

The biomass boiler is fuelled by a combination of different types of wood by-products produced as part of the sawmill operations; all of which would attract a different value if sold on. The wood fuel philosophy for the biomass boiler was to use up all of the lower value by-products first and so the bulk of the fuel comprises bark and butt chips – this is then ‘topped up’ with some higher value spruce chips to provide the total annual wood fuel required. A biomass boiler that could accept a wide range of wood fuel was specified to facilitate this. The moisture content of the wood by-products can vary considerably and so the wood is oven tested on a daily basis to ensure ongoing suitability. The biomass boilers were specified to accept wood fuel with a wide range of moisture content so any action required will be rare, however, if the moisture content is found

to be too high, the woodfuel would need to be stored for a short time to allow it to dry out before being moved to the fuel store, with any deficit in wood fuel topped up with the other feedstocks.

The boiler house includes a 200m3 fuel store, comprising a moving floor extractor with a chain conveyor system for transport of the wood fuel to the two feed augers to fuel the boilers. The wood is chipped and tipped into the fuel store by the on-site handling vehicles. The constant availability offered by the on site fuel resource and on-site fuel handling vehicles mean that a relatively small fuel store can be used. The potential variability of self-supplied woodchip from the different on-site by-products and total volumes involved in the fuel store required a robust fuel delivery system that a walking floor provides. The walking floor fuel delivery system is shown below.

The existing oil boiler is fully integrated into the heating system. Although the system is designed so that the biomass boiler and thermal storage can supply 100% of demand, the auxiliary oil boiler can be brought online as required in the event of infrequent demand spikes, a biomass system failure or for planned maintenance periods.

Walking Floor Fuel Extractor

Biomass case study

The biomass heating system and auxiliary boiler are fully integrated via a bespoke fully automatic control and monitoring system that ensures the temperatures supplied to the heat distribution network are as required for kiln operation, whilst minimising heat losses and maximising seasonal efficiency of the biomass plant.

A breakdown of the project costs is shown below:

A summary of the boiler performance over the two month period following commissioning and handover is shown below. This shows that the boiler is operating at an efficiency of 81%; which is extremely good when considering the nature of the mixed biomass fuel stock and its varying moisture content.

A summary of the main project facts are tabulated below. The performance and savings of the biomass boiler system are compared against the alternative approach of the 8,830MWh/yr thermal demand of the increased kilning level being provided by 84% efficient oil boiler.

Fuel Use (tonnes) 840

Total Fuel Input* (kWh) 1,651,777

Total Heat Output (kWh) 1,346,000

Seasonal Efficiency 81%

Component Unit Note

Biomass Boiler Installation

2 x 3MW Installed by KIV.

Auxiliary Plant 4.85MW Using heating oil.

Biomass Fuel Source Self-supply Wood co-products from onsite timber processing.

Biomass Fuel Consumption

5,660 tonnes/yr

At circa 55% moisture content.

Biomass Fuel Expenditure

£130,200 £/yr Cost for onsite chipping – £23/tonne.

Biomass Heat Output 8,830 MWh

Fuel Store Size 200 m3

Co2 Emissions Saved 2,400 t/yr Based on expanded kilning capacity.

Installed 2010/2011

Capital Cost £1,614,385 Includes installation of additional kiln.

Annual Savings of Fossil Fuel

1,002,555 litres/yr (using 10.4 kWh/litre).

Annual savings on Fossil Fuel Costs

£477,402 Based on increased kilning capacity.

Estimated Annual RHI Income

£88,300 RHI scheme to launch in November 2011.

Payback 4.3 years This payback does not include any revenue from additional kilning output.

Project Costs for 6MW Biomass Boiler Plant

6MW Wood chip boiler and ancillaries £723,100

Fuel feed system £94,800

Accumulator tanks £29,500

Flue system £14,165

Transport and delivery £28,080

Boiler house and civil works £185,300

Mechanical installation £287,500

Electrical installation £69,200

Wood chip store £92,600

Design and project management £57,720

Miscellaneous £15,120

Total project costs £1,597,085

* Calculations of net calorific value of woodchip fuel have been produced from EN303-5:1999.

February 2012