Solar & Wind Technology Vol. 7, No. 1, pp. 15-19, 1990 0741-983X/90 $3.00+.00 Printed in Great Britain. Pergamon Press plc

GROWING, HARVESTING AND MARKETING COPPICE EUCALYPTUS TREES FOR FUELWOOD

RALPH E. H. SIMS Massey University, Palmerston North, New Zealand

(Received for publication 1 February 1989)

Abstract--Several species of short rotation coppice trees can be considered for production of fuelwood for both the domestic and industrial markets. The preferred species in most districts of New Zealand is eucalyptus. Planted at 5000 trees/hectare, the first harvest after three years yields around 60 t/ha air dried. Subsequent harvests are likely to be at two-yearly intervals subject to further evaluation. The cost analyses of establishment, production and processing including transport, storage, and distribution costs, are discussed. A market assessment of domestic firewood is summarized along with a technique to compare the costs of competitive fuels.

INTRODUCTION

New Zealand has good reserves of coal and large natural gas fields with gas reticulated widely through- out the North Island and liquid petroleum gas avail- able in both islands. It also has an excellent climate for crop growth so that biomass fuels cannot be neglected as an energy resource. With the devel- opment of efficient two stage, slow combustion, wood burning stoves, many homes are heated by wood. Typically between 1 and 2 tonnes of wood per year would be burnt per insulated household depending on locality. Currently domestic firewood is sourced mainly from sawmills, and timber processing residues and waste wood from farms [1] but these supplies are now dwindling. Consequently there are firewood supply constraints in the main urban areas [2].

Industrial fuels for heat and steam generation are commonly natural gas or coal. The anticipated life of the natural gas resource at current usage however is only 10-15 years and coal, although plentiful, will become more expensive to mine in the future. Hence it is timely to consider fuelwood as an option. In addition the agricultural industry is currently seeking alternative land uses away from traditional products and coppice tree production is one such option.

A recent development in industrial fuelwood pro- duction relates to potential environmental benefits. Many rural industries such as meat works have effluent disposal problems. Adjacent pasture land can- not always cope with the effluent spread on it and groundwater pollution occurs even where areas of land of up to 100 ha are available. A project has begun to study the growth of coppice trees on these areas with the intention of reducing the pollution whilst

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producing fuel for use in the factory. Similar inves- tigations are being undertaken for sewage disposal near towns and villages [3].

AGRONOMIC PRODUCTION

The comments and costs given below are based on experience from research and commercial activities relating to this subject.

Eucalyptus species are currently favoured over aca- cia or salix due to the yields obtainable and suitability of the wood for combustion though all three species are being studied. Although agronomic studies are far from complete it is current practice to plant in 2 m rows at 1 m spacing (5000 trees/ha) to maximize dry matter production per hectare per year. Favoured species are Eucalyptus botryoides, E. sali#na, E. camaldulensis and E. Nitens. Seedlings can be pro- duced direct from seed in root trainers for $650/1000 (NZ$1 = US$0.65). Tissue culture techniques have not yet been investigated. Land can be leased for $600/ha/year; cultivation costs around $350/ha and transplanting of tree seedlings about $125/ha. Insec- ticides ($80/ha/application), herbicides ($50/ha/ application), and nitrogenous fertilizer ($80/ha/ap- plication) must be applied as required. Using these costs (based on actual agricultural contracting charges including labour) and adding 10% to the total for contingencies and management costs, total estab- lishment costs in the first year are around $4500/ha.

Subsequent maintenance costs would be around $600-$1,500/ha/year depending on how much fer- tilizer is required and how many disease, insect or weed problems arise [4].

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The optimum number of stems left to regrow after harvest depends on the nature of the product required and is subject to continuing research.

HARVESTING

The first harvest occurs after three years with sub- sequent harvests anticipated at two-yearly intervals. Moisture content at harvest is typically 50-60% (w.b.). A one-row harvester (purchased from Canada along with world licensing rights) operating at 2.5 km/h would cover 0.1 ha/hour. Capital cost of the harvester and a 55 kW tractor is around $100,000 and the wages for an operator are currently $11/h (plus 100% overheads). Hand felling with chainsaws is a possible alternative costing around $550/ha but will- ing labour is hard to find for large areas. The trees are cut in early spring and left in bundles over the field to air dry. They must be collected within 6 to 8 weeks to avoid damage to the regrowing coppice shoots. Moisture content reduction to around 25% m.c. dur- ing this period has been measured but this is yet to be confirmed for colder regions of tile country.

Average weight of a tree at harvest is approximately 20 kg (maximum 35 kg) reducing to 12-14 kg after drying. This is equivalent to 48 t dry matter/ha or 60 t/ha air dried yield. Returns to the grower are around $90/air dry tonne less transport costs to the processing plant. Since there is only a limited period available for harvesting it is assumed each harvester will only be able to work for 400 h/year giving a service capacity of around 40 hectares.

Collection A forwarder or grapple ($10,000) attached to the

same tractor as used for harvesting can be used to collect and accumulate the bundles into half tonne loads of around 30-35 trees. At l0 km/h and an aver- age transport distance of 600 m to a central processing site on a 40 ha block, the cost would be around $57/h. At 11 bundles/h and 15 h/hectare this would equate to $855/ha, with the tractor working for around 1200 h each year.

Processing The chosen process depends on the desired product

combination. It is important that the whole tree be utilized to maximize returns, the smaller branches and leaves consisting of up to 50% of the total biomass yield.

Possible options include the following.

(i) The whole tree could be shredded then recom- pacted into briquettes which are denser than the orig-

R. E. H. SIMS

inal wood, easy to stack on pallets, and clean and convenient to handle. This latter system would require a two stage shredder with 80 kW electric motor which could handle 8 trees/rain, plus a generator and con- veyors costing $100,000 in total. It would work for 400 h/year to service one 40 hectare block and could be made mobile to be used at several different sites thereby spreading the capital cost. A 1 tonne/h hydraulic compactor working for 2400 h per year would also be needed ($170,000). This option is the one considered in detail in the economic analysis below as full analyses of options (ii) and (iii) are not yet completed.

(ii) The trees could be first fractionated into stem wood (being around 150-200 mm diameter) and resi- dues consisting of the branches and tops which would then be shredded and briquetted. The stem wood would be cut into billets.

(iii) The stem wood could be utilized for short pulp fibre production ['or high quality paper, and the resi- dues shredded and compacted.

Such dual products as outlined in options (ii) and (iii) would enable the fixed capacity of the processing equipment [as detailed in option (i)] to cope with twice the area of crop produced.

Storage and distribution For the domestic market the briquettes would need

to be packed and stored on wooden pallets in 0.5 tonne loads and then transported to the local market say an average distance of 10 km. Approximately 2400 pallets would be required for a 40 ha crop which at $15 each is a further capital outlay of $36,000. Return deposits would be required. Storage indoors (cal- culated at $~. [0/'m: floor area/year), packaging (taken as $2/pallet) and transport costs (at $0.16/km/tonne) must be included.

In addition to all these above costs a further 10% for contingencies and management was allowed.

COST ANALYSES

Detailed commercial analyses of a system based on product option (i) above have been undertaken for a 5 year production period. They are summarized here and presented in simplified form. Full details are avail- able on request. The basic assumptions used for the cost calculations are given in Table 1. Table 2 gives a summary of typical costs for planting a 40 ha block of trees in spring 1987 which will yield 60 t/ha air dried in 1990.

A grower receiving $90/t will be close to breaking even after first harvest depending on yield and input

Eucalyptus trees for fuelwood 17

Table 1. Basic assumptions used for cost calculations

Cost of capital 20% interest Insurance 0.5% of capital Fuel $0.70/1 Electricity $O.08/kWh Oil 15% of fuel Labour (+ 100% overheads) $22/h

Harvester Tractor Shredder Compactor

Repairs (per annum) 8% 8% 4% 8% Life (year) 10 8 10 5 Resale value $5000 $8000 $5000 $5000

Inflation and tax were taken to be zero to simplify the calculations. All yields and costs err on the conservative side particularly where "guess-

timates" had to be made.

costs. Subsequent harvests should return reasonable profits.

It is thought that at least five harvests would be taken before replanting the trees became necessary

due to natural mortality. This depends on the damage to the stump during the cutting operation or sub- sequent collection o f the stems and on disease infes- tation by such fungi as silver leaf at this stage.

Table 2. Typical costs for planting a 40 ha block of trees in spring 1987

Establishment $4593/ha Maintenance year 1 $947

year 2 $772 year 3 $682

Harvest--winter 1990 Collection Shredding and conveying

$6994/ha = $840/ha =

$116.60/tonne air dry $14.00/tonne air dry $18.10 $36.30

Total cost for industrial fuel

In addition for the domestic market the following costs must be added

Compaction and handling Storage and distribution

$185.00/tonne

$57.60/tonne $18.20

Total Maintenance year 4 $1409/ha

year 5 $772

$260.80/tonne production

Harvest--winter 1992 Collection Shredding and conveying

$2181/ha = $36.50/tonne $840/ha = $14.00

$18.10 $36.30

Total cost for industrial fuel $104.90/tonne

For the domestic market the additional processing costs must be added as before

Compaction and handling $57.60/tonne Storage and distribution $18.20

$180.70/tonne product

t8 R . E . H . SIMs

Marketing It is important to determine the potential markets

before planting the trees. Sites need to be chosen alongside the market to minimize transport costs. In New Zealand a shortage of domestic firewood is evi- dent in many urban areas. For industrial purposes the coppice plantation should be sited alongside the combustion plant wherever feasible.

Even where electricity, natural gas, heating oil and coal are available many consumers prefer burning wood for a variety of reasons. In urban areas a recent trend is towards packaged firewood purchased in small amounts giving convenience and freedom from storage problems. Retail prices can reach over

$600/tonne. Whether consumers will readily accept briquettes or are prepared to pay a premium for more natural looking logs has yet to be determined.

A technique to enable the costs for a range of space heating fuels to be directly compared has been developed (Fig. 1). Capital investment costs are not included. The method allows for the various efficiencies between fuels and appliances to be allowed for and can accommodate fuel price variations between regions or over time. It shows that wood at $100/tonne competes well with most fuels in New Zealand other than natural gas though gas is not always available. At a comparable retail price of around NZ$300/tonne, necessary to recoup the initial

18̂ ~sse3 ~" =Iss.10

40 FILL 90 18

s,-roN; E 't "t / 1 , 1 1 1 / o/L c,L

1 5 '

W 5 100.

100 S/BAG (50kg) 30 l c/kWh /

$/GJ 12 USEFUL

HEAT S/T NE 9 7 OUTPUT 1 1

8 10 300 8~ ~ 220 ]

20 9 - 200 t ,RD 7 • 60 /

8" 180 ] INEOR 5- 7 I-

8 50' 160 • ]

200 5 4 ! 1404 6. c/CMJ 5. 120 ]

3 10 100]

100 EXAMPLES 6080 l

• ,,, CHRISTCHURCH PRICE8 JULY 1987 (WORLEY,1987) 40

4(- = WELLINGTON-HUTT VALLEY PRICES APRIL 87 (MINISTRY OF ENERGY,1987)

1 2 s 4 5 6 r 8 o 1o 11

~>= A=~ ", , , 5,,, >-~ ,->'= ~ = "'-~ ~ '~ <

, , , : = : ~ z

SEE APPENDIX 1 FOR DETAILS

Fig. 1. Comparison of useful heat output costs from a range of fuels allowing for combustion efficiencies (see also the Appendix).

Eucalyptus trees for fuelwood

investment capital after the first harvest, the com- petitive advantage is less evident. However it is un- likely users of wood burning stoves will change their appliances just to save fuel costs. Moreover electricity prices are anticipated to rise significantly in the next year or two. The current price being paid for bagged wood gives confidence that in urban areas there is sufficient demand for such fuels.

CONCLUSIONS

Eucalyptus trees can be grown intensively at high populations to produce good yields ofbiomass. Such a resource can be utilized in several ways with fuelwood being a prime product. It can be used for both dom- estic and industrial heating purposes and if managed properly plantations can provide an annual supply of fuel for many years before replanting becomes neces- sary.

Production costs will vary with input requirements, methods of harvesting and processing and yields obtained. On a commercial scale the economics

19

appear reasonable. It is possible that on a smaller scale for say supplying a village with fuel and using hand labour rather than machinery that coppice euca- lyptus trees are worthy of further detailed inves-

tigations.

REFERENCES

1. R. E. H. Sims, P. Henderson, G. A. Martin, I. G. McChesney, N. Rennie and C. J. Studman, On-farm energy supply and conservation. New Zealand Energy Research and Development Committee. Report 98 (1983).

2. Copeland Brown & Co. Ltd, Domestic market potential for solid fuel burners. New Zealand Energy Research and Development Committee. Report 84 (University of Auckland, Private Bag, Auckland) (1984).

3. J. N. Buddle, G. P. Horgan and C. J. Terlesk, Forest management economic analysis: costs of establishing and harvesting sewage irrigated energy wood plantations. Forest Research Institute Report 0256B/DMH (1987).

4. R. E. H. Sims, Fuelwood production from coppice euca- lyptus trees grown in New Zealand. Handling and pro- cessing of biomass for energy. Proc. Workshop Co-oper- ative Network of Rural Energy. Food and Agriculture Organization of the United Nations, Hamburg, in press.

APPENDIX

Fuel description, net energy value and combustion efficiencies used to construct effective heat energy for charts in Fig. 1. Effective heat energy = calorific value x burning efficiency

Usable heat units

1 Wood Air dry, 20% moisture content (wet basis) : 14.7 MJ/kg 8.82 MJ/kg Enclosed 2-stage stove : 60% efficiency

2 Wood Air dry, 20% moisture content : 14.7 MJ/kg 2.20 MJ/kg Open fire : 15% efficiency

3 Coal Ohai : 23.3 MJ/kg 13.98 MJ/kg Approved coal burner (Christchurch City Council) : 60% efficiency

4 Coal Waikato : 21.7 MJ/kg 3.26 MJ/kg Open fire : 15% efficiency

5 Electricity Domestic rate: 3.6 M J/kWh 3.6 MJ/kg Radiant heater: 100% efficiency

6 Electricity Off-peak : 3.6 M J/kWh 2.88 MJ/kW Night stove : 80% efficiency (due to unwanted heat wasted)

7 LPG Cylinder refilled : 45.8 MJ/kg 34.45 MJ/kg Flue heaters : 75% efficiency

8 Kerosene Supply own container : 34.4 MJ/L 30.96 MJ/L Portable fluelless heaters : 90% efficiency (ventilation essential)

9 Home heating oil Delivered in bulk : 37.4 MJ/L 22.4 MJ/L Pressure jet burner/air heater/ducts : 60%

10 Wood Bagged manuka, air dry 20% moisture content: 14.9 MJ/kg 447 M J/bag Enclosed 2-stage stove : 60% efficiency 50 kg bag

11 Natural gas Blended Maui/Kapuni: 36 MJ/m 3 25.2 MJ/m 3 Flue heater : 70%