1.0  Project creation

 

1.1 INTRODUCTION

Waste to Energy (WTE)  projects are complex, and their economic success depends on a variety of aspects that influence the technical and economical feasibility. It is therefore important to consider the relevant technical, organizational, economical and financing issues at an early stage when developing WTE  projects. In this first phase, project creation, a number of relevant questions have to be answered positively:

■ What kind of technique will be used? Is the existing infrastructure of the desired location (a dumpsite or open spaces, for example) used in an optimal way?

 

■ What types of facility are required? For example, is it technically possible to feed  in the electricity using the current grid connection? Can the produced heat be used?

■ Is it possible to use all the waste materials from within a close radius, does it need to be sorted, segregated, reduced, recycled and reused? 

■ How can the final waste residue be disposed of, can it be re-processed into useful by-products, such as fertilizers, fuel briquettes, construction aggregates, re-manufactured into building material blocks and sheets and and use as earth-fill for shore reclaimation?

■ Is the project economically feasible? 

■ Is it likely that the necessary permits will be obtained? 

Economic feasibility is the basis of every commercial project. In the creation phase, a cost analysis at a basic level is sufficient. In calculation, method  is presented for estimating the economic feasibility of a WTE. If this and  the other questions have a positive outcome, the project development can continue with the next phase: a feasibility study, including a detailed economic analysis based on  updated quotes from suppliers.

 

 

IS THE WTE PROJECT  ECONOMICALLY FEASIBLE?

The economic feasibility of WTE depends on various factors. The feed-in tariff for electricity from biogas and possible subsidy schemes are determined mainly by government, but the following factors are waste path processes flow, company or project dependent:

■ Amount of waste. Increasing the amount of waste will lead to economies of scale: for example, doubling the amount of waste to be digested will increase the investment costs, but will not double them, this is in the case of Anaerobic Digestion (AD) waste processing. To completely minimize waste residue Plasma Destruction and Devolitization is highly recommended, where heat and synthetic gases produced are utilized for steam turbine power and fuel cell power generation and by-products are re-usable.

■ Composition of the manure and waste matter. The type of manure (from cattle or pigs, household and commercial waste for example) determines the biogas yield, but the dry matter in the manure is also an important factor. If the manure is relatively wet, a large digester is required for a small biogas yield and for solid waste, Thermal Combustion processing is applied. In practice, the dry matter content can be influenced to some extent by reducing the water use when cleaning the stables.

■ Availability of other digestible organic material (co-substrates). Co-digestion of other organic materials will increase the economic feasibility. Organic materials such as agricultural residues (possibly from own farm) or residues from the food processing industry have high specific biogas yields compared with manure. In most cases these residues can be obtained at low or negative costs.

■ Consumption and cost of electricity use of own company. The electricity that is produced can either be used on site by    the company, or fed into the electricity grid. This consideration will depend on the tariffs of both, but also on   the sustainability goals of the owner of the WTE  plant. 

■ Heat demand of own company or nearby neighbours. The heat produced with the biogas can satisfy a local heat demand. However, transport of heat is relatively expensive. So the final heat demand should be within a small radius of the heat production (a maximum of 200 m as a rule of thumb, but preferably less).

■ End-use of (co)digested waste. The number of directly available nutrients is higher in (co)digested manure than in non- digested waste. It is possible to save more than 10% of the costs of nitrogenous fertilizer. But in practice this advantage is only possible when the substrate is used on one’s own land. Buyers of manure are not likely to pay more for it to be digested.

■ Financial status. It is advisable to think about the financing of the project at an early stage. If the creditworthiness of the investor is high the interest rate of the loan required to finance the investment can be lower. Also, the amount of the investment that can be obtained by means of a loan will be higher. One possible option for financing a project is through Foreign Assistance, and from a local leasing company or an electricity company.

 

1.2 REQUIRED PERMITS

In general, building permits and environmental permits are necessary for WTE  installations. It is advisable to check whether permission is needed to use the (co)digestate as a fertilizer. It should also be checked whether there is a zoning plan for the desired location of the digester. For each permit it is important to check with the respective legal authority on their general attitude towards Anaerobic Digesters (AD), and how long the permission process will take.The relevant regulations vary from country to country. A detailed description of these and other required permits is given.

 

 

GRID CONNECTION

In order to feed the produced electricity into the grid, adaptations of the existing connection are usually required. In the creation phase of planning it is usually sufficient to know what types of extra facility will be necessary if a small CHP unit (20–150 kW) is to be connected to the grid.The owner of the grid can provide information on the conditions that the installation must fulfil, and on  the costs related to the necessary adaptation of the grid. It is advisable to contact the local grid operator at an early stage of the project. Usually the electrical equipment and the grid connection have to be executed by a registered electrician.

 

1.3  GO/NO GO

At the end of the creation  phase one should be able to give a positive answer to the questions stated at the beginning of this phase. A first impression of the desired installation, including capacity, and the outline of the feasibility has been sketched. At this point the project can  move to the next phase: the feasibility study.

 

 

2.0 Feasibility study

 

2.1 TENDERS FROM SUPPLIERS

There are many suppliers of  WTE  installations. Requesting tenders is a good way to get an idea of the differences in technique and investment costs between the various suppliers. A tender can be turnkey, offering an operational installation. Also, activities that are required to operate an anaerobic digester legally may be included. Alternatively, some of these things can be done on one’s own account. Often parts of the construction, obtaining permissions and  making arrangements with the grid operator are done by the company who wants to set up the WTE. When requesting a tender it is important to be clear what type of installation is wanted and what should be included or excluded. This can be spelled out in a specifications, which should include the following minimum requirements:

■ annual amount of waste and manure for anaerobic digestion, for thermal combustion and for gasification

■ composition of the manure and waste (or at least the dry matter fraction)

■ annual amount of co-substrates, physical description and composition

■ existing infrastructure that can be integrated with the AD installation, including manure storage systems that can be used for storage of the (co)digested manure, and existing buildings that can be used or existing equipment such as  manure mixers or pumps

■ description of the soil or the foundation on which the WTE plant and digester will be installed

■ heat demand that will be satisfied by the heat from the CHP, such as the stables, the (private) house or other.

It is also clear that the installation  needs to obey the applicable standards regarding safety, emissions and  noise.The supplier should be familiar with these standards.

On the basis of the main components of a digester and their size it is also possible to form one’s own estimate of the investment costs for an  installation.The sizing of the components is worked out in  section..

 

2.2 PERMITS

In the creation  phase it was sufficient to find out about the general attitude of the legal authority towards WTE and AD. In this phase a further step has to be taken  and a request for a decision in principle has to be passed on. It is likely that a small description of the project with a sketch of the intended  result will be sufficient.

 

FEED-IN OF ELECTRICITY

Usually, most of the electricity will be fed into the grid, as this is economically more attractive. However, at some times – at peak hours, for example – it can be more favourable to use the produced electricity oneself. Also, in some cases it can be advantageous to have a larger CHP unit in order to produce electricity at peak hours only.This decision should be made on basis of the peak and off-peak  tariffs, the feedin tariffs, and the additional costs for the CHP unit. The electricity company involved could give advice in making this decision.

 

 

2.3 UTILIZATION OF HEAT

In the creation phase an inventory was made of the possible use of the produced heat. In this phase the heat demand  must be worked out in detail. As well as the size of the heat demand, its variation in time is important: for example, for households the heat demand  may be nearly absent in the summer. Also, the benefits of the heat use must be weighed against the costs of  heat  pipes.

 

2.4 CONTRACTING FOR CO-SUBSTRATES

If the farm cannot supply the desired amount of co-substrates (or manure) itself, external supply is necessary. In some cases this supply will be done on the basis of accidentally available residues. However, for a continuous supply of co-substrates it is advisable to conclude contracts with these suppliers. Important aspects that should be arranged in such a contract are: 

■ type of co-substrate (or manure) and amount

■ rate(s) and time of supply

■ specifications of quality (possibly in ranges), including moisture content, contamination (e.g. plastics, stones), nutrients

■ measurement of the deliverable (quantity and quality).Which (standard) methods  will you use for this? On what basis can you refuse a load? Assign a procedure that deals with these steps

 

■ duration of the contract.The longer the contract, the more continuity of the supply is secured. Also set down a period of  notice

■ price of the co-substrate. Prices can fluctuate annually: therefore it might be  necessary to negotiate a price every year

■ conditions of payment

■ liability.

 

 

2.5 DISPOSAL OF EXTRA NUTRIENTS

The extra nutrients resulting from the supply of co-substrate from external sources have to be used after digestion. If this can be done on one’s own farm land  it may not result in extra costs (apart from extra costs for transport to and applying it on the land). However, if there is no space left on one’s own land the extra nutrients will have to be bought by a third party. Additional contracts for this will be necessary.

 

2.6 SIZING

In the tender from the supplier the size of the various components should be specified. On the basis of the main components of a digester and their size, one’s own estimate of the investment costs for the installation should be made. The main cost components are the digester tank and its insulation, the CHP unit, the mixers, the pumps and the piping.

 

2.7 GO/ NO GO

With the information acquired in the feasibility study, the economic feasibility can be estimated using a calculation tool. If the economic feasibility is positive, and if the legal authority has given a positive decision in principle on the proposed anaerobic digester and thermal combustor, the project can be worked out in more detail.

 

3.0 Project preparation

 

3.1 SELECTION OF SUPPLIER

 

On the basis of the various tenders (from the feasibility study) a preferred supplier can be selected. With this supplier (or with multiple suppliers for the various parts of the digester), the terms of delivery have to be agreed. The following aspects are important to consider:

■ What exactly will be delivered? For example, what is the size of the digester? Are  the permits included? Are there possible additional costs?

■ What type of effort is required during construction (amount of time, required skills)? Costs can be reduced if the project owner provides labour to help during the construction of the installation.

■ What is the delivery period?

■ Product and process specifications

■ Guarantees for the project or the process (for example duration of guarantee, minimum number of operational hours, minimum yields)

■ The price of the offer, the period for which the offer is valid, and the index that can be used to adjust the price.

■ Terminating conditions: reasons to dissolve the contract.These should at least include the refusal of permits (or additional requirements by the legal authority that are unacceptably costly) and the failure of the project financing.

■ Possibilities for a maintenance contract. What exactly is included in the maintenance contract? It is advisable to have at least a maintenance contract for the CHP unit.

At this stage the supplier will have to detail out the installation (engineering). Specifications, a scale drawing, maps etc. are likely to be necessary for the permissions. The supplier may ask for reimbursement for this engineering.This can be deducted when the installation is commissioned.

 

3.2 PERMISSIONS

At this stage the permissions process can be started.The legal authority will tell you which documents are needed. In most cases the minimum requirements will be:

■ scale drawings

■ engineering calculations (e.g. mass flows, biogas and  kWh production, sound levels)

■ safety plan.

It is possible that there will be additional requirements. If these have high costs associated with them, the economic feasibility of the project can be endangered. For this reason, the plant should not be commissioned until the permissions have been obtained.

 

3.3 PROJECT FINANCING

During the permissions process the project financing can be worked out in detail. Possible subsidy schemes should be checked. As in most cases a loan will be necessary, it is wise to ask various financing institutions (banks or leasing companies) for quotes. An accountant or a financial/legal advisor can give advice on the optimal legal structure (e.g. a corporation).

 

3.4 FINAL GO/ NO GO

On the basis of the detailed design of the installation, meeting all the requirements set out in the granted permits, the final economic analysis can be made.This analysis should show the annual cashflow over the lifetime of the project. As the project financier will check the cashflow, it is advisable to let an accountant control the calculations. If this final economic analysis is positive the project is ready for realization. Nonetheless, the following checklist should be considered first:

■ There are no misunderstandings between the supplier and the customer. It is clear what the supplier will deliver and what your effort will be.

■ The building site is reachable, the soil conditions are OK, and  the positions of existing wires and cables are known.

■ All permits are irrevocably granted.

■ All tasks are commissioned by written documents.

■ There is a working plan for the installation, including the connection of the separate parts.

■ Payment conditions are agreed upon with all the involved parties.

■ Approved construction plans are present.

■ The quality and safety plan  is present.

■ The building  plan is present

 

 

4.0 Project realization, commissioning and start-up

Once the final go decision has been  made, the project is ready for construction. In this section  the planning of the construction  up to the start-up of the installation is discussed.

 

 

4.1 Planning and construction

 

4.1.1 PLANNING

The companies that are responsible for the construction and the installation must have a clear plan containing the following data:

■ the start of the work, and the time planning in phases with corresponding milestones/deliverables

■ the supply of parts and materials

■ payments

■ O&M training, testing, completion and commissioning

The communication structure must also be clear beforehand.When and with whom will consultations take place, in order to discuss the progress and possible difficulties? Is there a building supervisor who should see to it that the installation  is in compliance with the specifications and  the legal requirements? There should also be a procedure to notice extra or less work at an early stage.

 

4.1.2 CONSTRUCTION

During the construction  the following things should be well documented:

■ specifications of the built installation (with possible differences from the original specifications)

■ test results

■ instructions for operation and maintenance and safety procedures (training of personnel)

■ results of the commissioning test

■ calculation of  the realized  investment costs

■ guarantees and quality certificates.

 

4.1.3 OWN CONTRIBUTION DURING CONSTRUCTION AND SUPERVISION

It is possible that the project owner will have agreed with the supplier to help during construction. Assistance in several activities is possible, such as insulating the digester tank, mixing cement and pouring concrete, unloading equipment, welding or gluing together of the digester tank, connecting pipes, wires etc. It is also advised that the project owner does a regular check of the progress of the construction.

 

4.2 Start-up

The start-up of the anaerobic digester is a crucial step in the project realization. During start-up the biological process of biogas production will commence.The bacteria that are responsible for this process are already present in cattle manure, but need to be added when pig manure is used. Over a period of 3 months the biogas production will gradually increase to its maximum. The composition of the produced biogas can fluctuate during this start-up period. The methane content will increase up to 55–60%.The sulphur concentration  in the biogas is high at the beginning, but will decrease once the (biological) desulphurization is operational. When the construction of the digester is completed,  it is advisable that the supplier supervises the start-up. After the start-up period the buyer can check whether the installation meets the specifications regarding  the biogas yield and electricity production.

The day-to-day activities that the operator of the plant will have to perform during start-up consist of:

■ feeding-in of waste or, if this is done automatically, the monitoring of  this

■ adding the co-digestates

■ monitoring the function of  the mixers

■ keeping a logbook with the daily inputs of waste and co-digestates, temperature in the digester, biogas yield etc. It is important that the tasks of the operator are well documented. During start-up the supplier should still be responsible. When the methane content of the biogas is below 45% there may be a risk of explosion. If the methane content is higher than 45% the gas will burn without a pilot flame.The following safety precautions should be taken during the start-up period:

■ Prevention of sparks.
 
■ Disconnection of the gas conversion equipment from the digester.

■ During start-up the substrate has to be heated. As there is, as yet, no biogas to fuel the CHP unit, an alternative fuel or heat source is necessary.

■ If the CHP unit is connected to the heating system of, for example, a farm or a company, existing boilers can be used.

■ If the CHP unit offers the possibility of operating  in a dual-fuel mode (for example, if it can operate on either biogas or diesel), the secondary fuel can be used to fire the CHP unit.

■ A burner fuelled by diesel, natural gas, propane or another fossil fuel can be used temporarily. When fossil fuels are also being used to fire the CHP unit, the produced electricity can’t be regarded as fully sustainable. If this electricity is to be fed into the grid, discuss this issue with the electricity company that will buy it. In some cases where organic material is co-digested, it can be possible that the environmental permit requires samples of the co-digested material. It is advisable to have samples analysed already during the start-up of the digester. It should be the  responsibility of the supplier of the digester to ensure that the composition of the input and output of the anaerobic digester during this start-up period complies with the regulations. In most cases the supplier will hand over  responsibility for the operation of the anaerobic digester to the buyer at the end of the start-up period. Therefore the buyer of the digester will have to ensure during start-up that the installation is operating in accordance with the guaranteed specifications, such as the biogas yield and the composition. The supplier must inform the user adequately about the operational aspects.

These include:

■ instruction on the daily routines (feeding of manure and/or co-digestates, mixing)

■ inspection of the process’s main parameters and indicators (reading out measuring equipment)

■ monitoring of the biogas yield and composition (sulphur content, methane content)

■ operation and maintenance of the biogas conversion equipment (CHP, burners, flare)

■ safety instructions: indication of explosion alarm, measures in case of exceeding limiting values and emergencies

■ monitoring and administration (possibly as a legal requirement)

■ settling of accounts with the electricity company regarding the electricity that is fed into the grid.

As a result of this guide the  user should be capable of operating and maintaining a WTE or  the anaerobic digester or any other kind of waste processing.

 

5.0 Operation and maintenance

After start-up of the WTE and digester, it has to be operated and  maintained.This section deals with the operational aspects of an anaerobic digester, under normal conditions and  in the case of a malfunction, as well as with the maintenance aspects.

 

5.1 Operation of the WTE digester under normal conditions

The bacteria in the digester will take care of the biogas production. It is the task of the operator to control the process conditions and to make sure that the CHP unit operates properly. In order to do so the following activities will have to be undertaken.

 

5.1.1 DAILY ACTIVITIES

■ inputting the manure and co-substrates into the digester tank

■ inspecting the engine oil

■ checking the fault display/lights of the switchboard cabinet

■ inspecting the water pressure of the heating equipment

■ inspecting the dosing pump of the desulphurization unit

■ monitoring the temperature in the digester tank

■ adjusting the mixing intervals in order to avoid a floating surface or deposition on the bottom; also ensuring that the interval allows the biogas to escape from the slurry gradually

■ inspecting all supply and drainage pipes for flow of the manure and co-substrates

■ inspecting the levels in the digester tank and  in the final storage tank

■ inspecting the biogas storage

■ recording the biogas yield and operational hours of  the CHP unit.

Other relevant aspects that should be registered are the biogas consumption of the CHP unit, the electricity production, the digestion temperature, the input of cosubstrate, maintenance activities, and any unusual incidents.

These activities will take about 30 mins per day. If co-substrates are fed into the digester manually, more time may be necessary.

 

5.1.2 WEEKLY ACTIVITIES

■ Check the levels in the bags containing water from condensation, and empty if necessary.

■ Test the mixers.

■ Visually check the CHP unit and all its pipes.

■ Check the overpressure valve for functioning and pollution.

 

 

5.1.3 HALF-YEARLY ACTIVITIES

■ Inspect all bolts and flaps.

■ Bleed the central heating.

■ Inspect all electric equipment for damage.

■ Inspect underpressure safeguards.

■ Inspect all safety equipment.

 

 

5.1.4 YEARLY ACTIVITIES

■ Inspect the part of the installation that contains biogas for damage, leakage and corrosion.

■ Test the fire extinguisher(s).

■ Check all liquids for drying up or frost resistance.

 

References:

Planning and Installing Bio-Energy Systems, James A. James LTD, UK

 

TIP: To plan a WTE project, make sure it is within the confines of the Clean Development Mechanism- Project Design Document (CDM-PDD) criteria to qualify for a Certified Emission Reduction (CER) Carbon Credits.

For Foreign Grant or Loan Assistance on WTE project, contact:

 

The U.S. Trade and Development Agency (USTDA).

1000 Wilson Boulevard, Suite 1600,

Arlington, VA 22209-3901, USA

For Southeast Asian Countries:

 

The World Bank and

 

The Asian Development Bank

 

For a comprehensive WTE project, consult with us:

 

 

ENGR. JUNE A. YASOL

 

Alternative and Renewable Energy Consultant

 

Garbage Power Plant Systems (GARPPS) Designer

 

Philippines

juneayasol@yahoo.com

+639208371042