Marginal costs for the wood gasifier system
a) The capital cost
The marginal capital cost can be calculated by the annuity method if the capital investment and the economic lifetime of the gasifier system can be established.
The capital investment can be estimated from a recently converted Ford D-truck used for tests in Sri Lanka, which has been fitted with a gasifier system similar in size to the standard F-5/80-150 gasifier.
Table 3.19 shows how the different items of expenditure add up to the total conversion cost of about US$ 11000. This obviously is the conversion cost for a single vehicle converted in Sweden at a high labour cost (14.8 US$/h). It is quite clear that the labour cost is important since the manufacturing labour and fitting costs account for over 70 percent of the conversion cost. To illustrate the impact of a lower labour cost, Table 3.19 also shows the estimated conversion cost in a developing country with labour costs of 2 and 0.5 US$/h. In these estimates it is assumed that the time required is twice as high as a result of less well equipped workshop facilities and that the material costs are 10 percent higher. The conversion cost under these assumed conditions would be about US$ 5300 and US$ 3600 respectively.
With an assumed economic lifetime of six years and a real interest rate of eight percent, the annual capital cost for the gasifier system will be 21.6 percent of the capital investment.
b) Service and maintenance costs
Based on the experiences presented in section 3.2.4, the extra labour to keep the gasifier plant in operation can be estimated as 0.3 in/operating hour. The resulting cost will obviously depend on the labour rate, see Tables 3.20 and 3.21. The maintenance cost has-been assumed to be five percent of the capital investment for each 1000 operating hours. This leads to an estimated maintenance cost for operation in Sweden of 0.55 US$/operating hour, and 0.18 US$/operating hour in a country with a low labour cost.
For the economic evaluation of the wood gas truck, it will be necessary to consider the reduced load capacity and the longer distance travelled for a given load. The service and maintenance costs of the truck and engine will be assumed to depend on the annual driving distance according to Swedish experiences. For 60000 km/year it will then be 0.66 US$/km, for 30000 km/year 0.80 US$/km and for 1500 km/year 1,40 US$/km.
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Table 3.19 Cost of converting a vehicle to wood gas operation
1/ At labour wages of 15 US$/h. |
2/ These estimates do not appear unreasonable in comparison with costs reported for somewhat simpler systems manufactured in Brazil (750-2000 US$) and Sri Lanka (1000 US$).
c) Fuel costs
Fuel costs will be calculated assuming dual fuel operation and a fuel consumption for the tractor according to Table 3.13 and for the truck according to Table 3.16.