Chicken runs provide the fuel for Fibrowatt’s global ambitions

21 August 2000

Buoyed by a year’s successful operation of its chicken litter fuelled power plant, at Thetford in the UK, and boosted by significant investment from the Kelda Group, Fibrowatt Ltd is now set to move onto the world stage.

Fibrowatt’s third chicken waste-fuelled power plant, located on the borders of Norfolk and Suffolk in the UK, has now burned over 400 000 tonne of chicken litter and has worked up to a power production level of 38.5 MW of electricity during its first year of successful operation. The total cost of the project was $118 million. It is a further and more commercial development of the Kelda Group’s earlier plants at Eye in Suffolk (10 MWe) and Glanford (13.5 MWe) near Flixborough on Humberside.

Fibrowatt is now negotiating projects in many parts of the world, including North America, where a new company Fibrowatt LLC has been formed, in Italy (in association with Sondel), Japan (in co-operation with Marubeni), Belgium and the Netherlands.

Sondel, the electricity utility arm of the Falck group which took a 25 per cent equity stake in Fibrowatt in May 1997, has negotiated power purchase agreements with ENEL for plants near Venice (12.5 MWe), near Verona (35 MWe) and in the Emila Romagna plant (20 MWe). Further discussions have also taken place in Germany, France and Ireland.

Fibrowatt LLC is a joint subsidiary of Fibrowatt and First Renewables. It is estimated that the USA produces more than 20 million tonne/annum of poultry litter which is enough to fuel some 40 plants the size of the Thetford facility. The company is working on projects in five of the leading poultry producing states – Minnesota, Maryland, Delaware, Arkansas and North Carolina.

In February 2000, Kelda, the new holding company for the Yorkshire Water Group – well known for its pioneering ARBRE coppiced willow wood gasification power plant in Yorkshire (see MPS January 2000 p 51) – made two major investments in Fibrowatt Ltd. First, an immediate injection of some $9 million working capital in return for an initial equity stake of 31 per cent with an option to take control in the future by acquiring further shares under certain conditions. Second, an investment of some $4 million in equity and loans in exchange for a 51 per cent stake in the new Fibrowatt company in the USA.

Kelda’s investment was made by its subsidiary First Renewables – a new company which has been set up to promote, develop, and use sustainable energy resources. Kelda is an infrastructure group operating in Europe and North America with interests in water services, environmental services, waste management, energy projects and land development.

Thetford power station

Construction of the Thetford power station commenced in August 1996; the plant started operating in October 1998 and was handed over to the owners on 25 June 1999. It was shut down in October 1999 after its first year of operation, during it which it had effectively demonstrated the system’s technical and economic viability. The opportunity was taken to incorporate into the system revisions and process improvements largely aimed at further increasing availability and back-end temperature. Recommissioning took place in February 2000. It is now expected that the Thetford plant will exceed the load factors experienced with the first two plants of 91.3 per cent.

All three Fibrowatt plants to date have been built to substantially new designs, but successfully incorporate improvements and lessons learned from the other operating power stations. In each case, the company has been successful in obtaining sound project

finance (see Power Economics, January/ February, 1998 pp 41-43).

The fuel

Chicken litter is a by-product of the broiler poultry industry consisting of poultry droppings, wood shavings, straw and other bedding material. The poultry are kept in large open-plan houses on a bed of deep litter. The litter has a calorific value generally about half that of coal and has a moisture content of between 20 and 40 per cent. It is said to be in the interest of the poultry farmer to keep the moisture content down to about 30 per cent to ensure the production of healthy birds.

The litter, which is purchased from poultry farmers in Eastern England, has been valued as a high phosphate agricultural fertiliser. The ash from the combustion process, however, makes an even better fertiliser in some respects and can be sold on as an important commercial by-product of the project. Sold under the trade name Fibrophos, it contains no nitrate and is high in potash and phosphate. Sending the raw litter for combustion in a power generation plant is seen as a better approach to disposal than spreading it over fields at ploughing time since, apart from emitting methane into the atmosphere and contaminating ground water with run-off nitrates, it emits persistent unpleasant odours when spread on fields.

The plant site is located in an environmentally protected woodland amenity area close to the Norfolk city of Thetford near Norwich (see Figure 1). The plant is designed to have low visual impact by being screened by trees on all sides and by a high embankment between it and a public footpath along the banks of the Little Ouse river by which it is sited. The boiler house has been sunk into the ground so that it does not exceed the height of the trees and has been painted in a dark brown colour which very effectively camouflages it against the forest background. The one feature which is visible from some view points is the 110 m high chimney stack. Figure 2 shows the site plan.

The litter is delivered to the site in a continuous stream of large covered trucks which are unloaded in covered discharge bays in the fuel reception building under slight negative pressure, which prevents release of odour. There are six loading bays (Figure 3) into which incoming trucks are automatically directed by an advanced traffic control programme (see MPS, October, 1996, pp 23-25).

Between them, the three Fibrowatt power plants – Fibrothetford at Thetford in Norfolk, Fibrogen at Glanford in North Lincolnshire, and Fibropower at Eye in Suffolk – consume over 700 000 tonne/annum of poultry litter. However, the Glanford power station has recently switched over to the incineration of meat and bone meal arising from the cull of cattle over 30 months old for a 3 - 5 year one-off contract with the UK government.

The technology

The fuel does not lend itself so well to such advanced technologies as fluidised bed combustion or gasification. Relatively simple chain grates and spreader/stokers are used in the Fibrowatt plants. The simplified schematic in Figure 4 shows how the process works.

Although much of the technology is well proven without sacrificing much in terms of efficiency and emissions control, considerable advances have been incorporated into the Thetford plant (Figures 5 – 9). Fuel handling and ash removal are different. In the earlier plants, crane grabs were used to transfer the fuel from the delivery bunkers to the boiler feed, but in the Thetford plant spiral screw feeders transfer the litter to a conveyor belt (right) then to the steam generator where it is pneumatically transferred into the boiler furnace.

A Detroit Stoker grate is equipped with spreader stokers designed to blow the fuel into the boiler to ensure that most of the fuel is burnt in mid-air. Ash is pneumatically transferred into hoppers for mixing with a combination of trace elements to produce the commercial fertiliser product which provides an extra revenue stream for the plant.

Flue gas emissions control require the normal treatment for solid fuel combustion. Cyclones followed by a bag house are used to remove particulates and lime is added to reduce the levels of acid gas (HCl). Since the poultry eat considerable quantities of calcium and excretions are rich in ammonia, emissions of nitrous oxides and sulphur dioxide are naturally limited. External FGD scrubbers are not needed.

The litter is combusted at more than 850°C with a residence time of two seconds under conditions usually specified for the reduction of dioxin, but this is not needed to deal with the presence of furans which are chemically similar to dioxins. Some chlorine is present in the combustion gasses but the complete mechanisms to generate furans, dioxin or long chain polymers do not occur in the process. The steam generator, supplied by Foster Wheeler Canada Ltd, feeds steam at 450°C, 65 bar to a simple single shaft condensing steam turbine supplied by Ansaldo of Italy coupled to an 11 kV generator. Four steam bleed points are provided to supply condensate and feed water preheating.

The fuel intake hall measures some 30 m long by 10 m wide and has sufficient storage capacity for week-end deliveries to be generally unnecessary.

Fibrowatt’s architect-engineer was Foster Wheeler Energy and the turn-key contractor was Taylor Woodrow Management and Engineering Ltd. Civil, structural and architectural design was by Taywood Engineering. Rust Kennedy & Donkin – as it then was – acted as the power plant consultant. Elsamprojekt of Denmark was taken on as biomass consultant and ATL was taken on as the environmental noise specialist.

The boiler and emissions control systems were supplied by Foster Wheeler and the fuel handling by Birtley Engineering.


The project’s financial advisors – Impax Capital Corporation and Bank of America – put together the funding package.

Of the total project cost, Bank of Scotland arranged the $89 million project financed senior debt facility and co-underwrote it along with Westdeutsche Landesbank Girozentrale. A further six banks joined the syndication of the senior debt and Marubeni Corporation of Japan provided a $7 million mixture of junior and subordinated debt. The debt-equity ratio is a healthy 85 per cent and the finance is over a term of 12 years.

Catamount Energy Corporation, the energy investment subsidiary of Central Vermont Public Service Corporation, is an equity investor with a stake of 44 per cent in the project. Catamount has interests in five operating independent power projects in the USA, three of which combust biomass in the generation process, and it is also an equity investor in a gas-fired power generation project under construction in England. Foster Wheeler Energy Ltd also has a 5 per cent equity stake in the Thetford project.

As with the other two Fibrowatt plants, the economics of the project were assured by a Non-Fossil Fuel Obligation (NFFO) contract. The Thetford plant is the largest project to benefit under the UK government’s NFFO policy, which provides support for renewable electricity generation. Thetford’s NFFO3 contract gives the project an index-linked premium price for its electricity for 15 years after start-up. Normal staffing level is about 30 people.

The earlier plants were supported by eight year NFFOs but they lost some years of this owing to late commissioning and the fact that this phase of NFFO was only extended until the end of the nuclear power levy on which the NFFO’s were originally based. The fifth round of NFFO deals are likely to be very different again.

Chicken litter projects in the USA also seem to getting tied into complex nuclear legislation deals. Northern States Power is trying to get poultry litter into the USA biomass mandate with a view to covering as much as 50 MWe of its 300 MWe traded environmental impact allowance against permission to store spent nuclear fuel in its Prairie Island nuclear facility. It has been suggested that only 120 MWe of this had been fulfiled so far. A number of recent biomass proposals in North America appear to have been put aside due to uncertain economics, but the Maryland poultry litter project still seems to be on track.

The biggest operating cost is the purchase of the fuel, rather than maintenance which is relatively low. Across the world, the market price for this fuel depends on availability, environmental pressures and the quality of the fuel in terms of moisture and phosphate content etc. The colorific value is fairly consistent.

This form of biomass power is now virtually mature proven technology. It seems likely that such plants could very soon be profitably developed without the need for national government or international agency financial incentives or subsidies.

The Fibrowatt Group is now relying on its knowledge of fuel processing and handling, along with its proven biomass technology, to secure a place on the world stage in the development and operation of biomass-fuelled power stations.

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