Energy from waste and biomass
by W van Zanten, Novem, the Netherlands

Waste and biomass play a major role in the targets for sustainable energy in the Netherlands. This article looks at the prospects and challenges for these resources in meeting the Dutch government's goals.

Introduction

In the Netherlands, sustainable energy sources now contribute 1% to the total energy production. This contribution should rise to 10% in 2020, according to the Dutch government. Storage of energy from the wind and the sun is rather difficult, but biomass - which can be regarded as captured solar energy - can be stored. And, using today's technologies, electricity from biomass is much cheaper than electricity from PV systems. Since the conversion of biomass to energy is similar to the processes for gas and coal, utilities are perhaps better equipped to adopt biomass on a commercial scale than other renewable sources.

For these reasons, waste and biomass play a major role in the targets for sustainable energy in the Netherlands. We foresee that almost 60% of this contribution will originate from biomass and waste. This corresponds to 120 PJ/year (45 PJ waste and 75 PJ for clean biomass). To achieve this, about 4 million tonnes of biomass will be needed, far more than is available in the Netherlands. We will therefore need to utilise indigenous wood wastes and to import other biomass in the start-up phases, in which we implement and develop the biomass conversion technologies.

Different tracks

Waste and biomass are both sources of renewable energy but they are seen by the Dutch government as being on different tracks. Waste incineration plants generate electricity or heat as a by-product of their main activity which is to dispose of waste. Utilities initiate energy from biomass plants in an effort to generate clean energy. These plants can use cultivated miscanthus, poplar and willow as well as clean wood-waste and synthetics residues. Energy from waste in the Netherlands receives government grants of 50%, whereas energy from biomass is fully supported.

More energy yield

Existing waste incineration installations with their grate furnaces yield an electrical efficiency of about 23%. Only the Moerdijk incinerator reaches a yield of 38%, through a connection with a neighbouring combined cycle gas turbine unit.

Newer technologies, such as fluidised bed burners and gasifiers, promise higher efficiency/grade than furnaces. Whether or not these technologies succeed will depend on the economics of the new installations. At present, several projects are in operation or at a preparation stage, see Table 1.

Table 1: Thermal energy from waste/biomass in operation and in preparation in the Netherlands

Project

Nature

Size

Realisation stage

EPON, Nijmegen

Co-firing of wood waste

60,000 tonnes, 20 MW

In operation since 1996

EZH, Maasvlakte

Co-firing of biomass  pellets from paper  pulp and purification sludge

15 MWe 

Test firing from January 1998

NUON, Lelystad

Incineration of forestry thinnings and crops

1.5 MWe , 7 MWt

In operation in 2000

EPZ, Amercentrale

Gasification of polluted timber

30 MWt

Start-up early 2000

ENW, Prov. NH, Amsterdam

Experimental fluid bed gasifier for a diversity of biomass

15 MWe

Cancelled

Deltan, Zeeland

Gasifier of RDF waste

5 MWe

 

Gibas/Proav, Maasvlakte

Pyrolysis of shredder and RDF waste to produce industrial syngas

150,000 tonnes

 

Vagron, Groningen

Digestion of wet organic fraction

 

January 2000

Texaco, Maasvlakte

Gasifier of synthetics waste to produce industrial syngas

40,000 tonnes

 

Ecotheniek, Maarsen

Vacuum pyrolysis to produce oil from a variety of biomass

   

PNEM, Cuijk

Fluid bed of forestry thinnings and wastes

250,000 tonnes, 24 MWe

Mid-1999

UNA, Amste

Co-firing of purification sludge

15 MWe

 

Mega, Limburgrdam

Fixed-bed gasifier of forestry thinnings

1 MWe

 

Biomass processing

Another way of generating electricity is through gasification or pyrolysis of biomass. Gasification and pyrolysis are preferable to combustion because their efficiency is higher.

A major challenge is to obtain suitable biomass at a price-level which allows viable production costs. This problem arose when a 30 MW incinerator with gasification unit was planned in Amsterdam. The intention was to built an experimental installation to test different kinds of biomass. Calculations showed that the electricity from the plant would be priced at NLG 0.20/kWh (where NLG is the Dutch guilder) - far above the tariff utilities pay when buying electricity (NLG 0.08/kWh). The solution was to to build the installation in phases. The owner will build the incinerator first, and will have the option of adding on a steam turbine later. In the meantime, the gas produced by the gasification unit will be burned in a nearby power station, replacing some coal. The project will be viable immediately if the government proceeds with its plan to double the Ecotax from NLG 0.06/kWh to NLG 0.12/kWh.

The biomass market

New biomass energy projects put pressure on the 'market' in waste wood. Countries like Italy, the United Kingdom, Sweden and Germany already consume trainloads of wood for both energy production and the chipboard industry. In some countries, new energy projects have put pressure on the waste wood market. Waste wood is already traded in many counties for use in chipboard manufacture and to produce energy. Before many energy projects were developed, you could get about NLG 80/tonne for taking waste wood. Now, financial incentives for renewable energy projects in many countries have created a demand for waste wood, and it can cost up to NLG 60/tonne to obtain it.

Thermal processing of waste

Existing Dutch waste incinerators use an inclined grate furnace. Combustion takes place at about 850oC. Excess air is required to achieve good combustion, and flue gas cleaning is necessary.

Wood can also be gasified, using circulating fluidised bed technology, for example. Partial oxidation takes place at 1,200-1,600oC producing syngas which, after cleaning, can be used as a fuel.

Pyrolysis takes place at 400-800íC and in an oxygen-free atmosphere. The results are oil-like substances, syngas and char, all of which can be used as fuel.

A co-combustion project in a conventional power station is already in operation. The plant utilises about 60,000 tonnes/year of wood residue. Here, the waste wood is combusted in the same furnace as the coal, replacing about 5% of the fossil fuel.

For more information contact the CADDET Dutch National Team in Sittard

The CADDET Renewable Energy Newsletter is a quarterly magazine published by the CADDET Centre for Renewable Energy at ETSU, UK.

The articles published in the Newsletter reflect the opinions of the authors. They do not necessarily reflect the official view of CADDET.

Enquiries concerning the Newsletter should be addressed to Pauline Toole, Editor, CADDET Centre for Renewable Energy, ETSU, Harwell, Oxfordshire OX11 0RA, United Kingdom. Tel: +44 1235 432968, Fax: +44 1235 433595.