Dr G.S. Harris,
New Zealand Energy Research and Development Committee Introduction
The concept of energy farming was first mooted as a serious option for New Zealand in 1974 by research workers with an interest in the processing of biomass to liquid fuel and laboratory research commenced at that time. The overall concept of energy farming was studied during the formulation of 'Energy Scenarios for New Zealand'1, this work being undertaken mostly in 1975 and 1976. The Energy Scenarios were first published in 1977 and some further work undertaken in early 1977 was published in April 1978. Several workshops and seminars on energy farm- ing were held in the period 1975 to 1979.2
The Energy Scenario research clearly identified transport and the supply of liquid fuels for transport as being the most important energy supply problem facing New Zealand. It also pointed out the potential for energy farming but drew attention to the many unknowns related to this technology.
In 1977 the NZERDC which was already funding a considerable proportion of the research on energy farming (mainly fuel production research) decided to set up a group to study the technology as a whole — that is a systems study of energy farm- ing. The main objective of the study was to answer the question 'what is the poten- tial of energy farming in New Zealand?' This research commenced with a Workshop in September 1977 attended by research workers from Government, industry and the universities.
The systems study has been completed and the final report in two volumes has been subjected to an intensive review by a wide range of organisations and indivi- duals. A third volume — the critique — will be published early in 1980.
This paper briefly describes the research which has been undertaken on processing crops to fuel, the main results of the systems study with some of the criticisms which have been made and the present state of the recommendations of the study. No attempt has been made in the paper to separate out the issues involving ethanol as opposed to other transport fuels although it will be seen that there is considerable emphasis on ethanol in the New Zealand program.
It should also be noted that there is a wide range of New Zealand research on use of alternative fuels in vehicles which is not reported in this paper.
Research on Processing Crops to Transport Fuel
In this section there is a brief description of various research contracts on processing of feedstocks to transport fuel. These are the main projects but there are a number of smaller projects, especially in universities.
Ethanol
Acid Hydrolysis of Wood — Professor A.L. Titchener, University of Auckland.
This project examined sulphuric and hydrochloric acid hydrolysis of cellulose in radiata pine to sugar. It was concluded that use of dilute sulphuric acid was the best
* Previously published in the New Zealand Journal of Forestry, 24(1): 67-75(1979).
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method and then examined in detail the kinetics of the process under various condi- tions of temperature and pressure. The report is now being reviewed and should be published early in 1980.
Ethanol from Wood — Drs M. Uprichard and D. Whitworth, Forest Research In- stitute. A pilot plant capable of batch producing 5 litres per hour of 96 per cent ethanol from radiata pine has been constructed and is now in operation. Dilute sul- phuric acid is used for hydrolysis of cellulose to sugar. The plant includes a hydro- lysis reactor of capacity 0.25m3. It is expected that by the end of 1980 the plant will have produced sufficient technical data to enable a full scale plant to be designed.
Fermentation of Sugar to Ethanol — Professor A . P . Mulcock, Lincoln College.
This project has been mainly concerned with operating and optimising tower fer- menters and many tests have been conducted with a 7 litre laboratory fermenter using sugar from beet as a feedstock. The research workers have been closely in- volved in many aspects of research on production of ethanol from beet.
Coupled Fermentation of Crops to Ethanol and Methane — Dr R.A.H. Thornton, Cawthron Institute. At a laboratory scale, sugar solutions derived from beet and radiata pine were fermented in a linked system to produce ethanol and methane.
Tests were conducted to determine best operating conditions. The final report on this project is being printed.
Novel Fermentation Techniques — Dr V.F. Larsen, Massey University. This is a small project to evaluate packed bed reactors for their suitability as high rate ethanol fermenters.
Leaf Protein Concentrate and Ethanol — Dr R. MacDonald, Ministry of Agricul- ture and Fisheries. This is a new project involving the extraction of protein from lucerne or pasture, hydrolysis of the cellulose and fermenting the sugars to ethanol.
Other Fuels
Methane from Crops — Dr D. Stewart, Ministry of Agriculture and Fisheries. Many years of experiments on a wide range of crops such as maize and pasture have been conducted at the Invermay Agricultural Research Station and several reports pub- lished. A full scale methane generator is being constructed.
Fisher-Tropsch Synthesis — Drs W. Robinson and J. Cousins, Department of Scientific and Industrial Research. After several years of study of gasification, a small plant capable of processing up to one tonne of wood per day is being built.
The wood will be gasified in an air blown gasifier and some of the gas synthesised to oil using iron sand concentrate as the catalyst. This work is just commencing.
Research on other aspects of energy farming is less well covered. Some of the main recommendations of the energy farming study relate to the building up of the research on topics not now being researched. Mention should however be made of the trials currently under way to determine yields and costs of growing and harvest- ing sugar and fodder beet.
Objectives of the Systems Study
The study was concerned with use of energy farming to produce substantial quanti- ties of transport fuel. (The small-scale production of fuel, e.g. on farm methane, was not studied although such technology could well have a part to play in the future.) The study was undertaken using data which are fairly readily available, in 92
order to determine the potential of energy farming for New Zealand. The study was from the national point of view. If the concept of energy farming is eventually accepted for implementation, feasibility studies will be required for particular pro- cessing plants based on areas of land dedicated to supply biomass for that plant.
The study had the following principal components:
(a) Evaluation of land suitable and available for various crops;
(b) Technical, economic and environmental evaluation of agricultural crops as a source of biomass (sugar beet, fodder beet, maize, lucerne, oats, pasture);
(c) Technical, economic and environmental evaluation of forestry based on radiata pine;
(d) Evaluation of other crops on which there is less information than on the crops mentioned above;
(e) Technical and economic study of eight processing routes to produce liquid or gas;
(f) Environmental and social implications of energy farming.
Study of the use of alcohols in vehicles is now mainly covered by extensive contracts funded by the Liquid Fuels Trust Board.
Land Use
The concept of terrestrial energy farming involves using land to produce an agricul- tural or forest crop. The land so used needs to be both 'suitable' for the crop and 'available'. While criteria for 'suitability' can be written in terms of soil type, climate and topography, the criteria for availability depend on definition of an energy farming processing plant in a particular locality. For instance, only if farmers have an idea of the price to be paid for a crop will they say that some or all of their farm is 'available'. Hence, the study concentrated on land suitability. The results for maize, beet (sugar and fodder), lucerne and radiata pine are given in Table 1. For the first three crops, most of the suitable land is presently high value agricultural land.
This same land is suitable for radiata pine, but in addition, there is much marginal farm land, scrub, cut over native forest — land which could conceivably be used for a new more profitable activity such as energy farming.
Table 1. Interrelationships of Energy Crop Land Suitability (hectares)
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In general terms it can be stated that the area of land which is potentially available for energy farming using any of the crops — fodder beet, maize, lucerne or radiata pine — is well in excess of the land area which would be required to supply 100 per cent of the liquid fuel requirements in 2000. (Ministry of Energy projections of transport demand.)
Agricultural Crops
The study of agricultural crops has proceeded with the philosophy that any crop which is used for energy farming should be integrated into the existing farming situation. If energy farming were to proceed with agricultural products, then the existing farmers with their knowledge of particular crops and farming techniques would be required to change their method of management in only a comparatively small way in order to produce the energy crops. In many cases it is quite possible that stocking rates could be held at existing levels. In this way energy farming would be more likely to succeed.
The second point of philosophy in the study has been to minimise the energy inputs used in growing the energy crop. Generally, conventional technology and practices have been used, and no attempt has been made to minimise energy inputs through such new practices as low tillage cropping.
A range of crops has been studied and the energy ratios, energy yield and produc- tion costs for some are presented in Table 2. This table indicates that fodder beet is the best of the crops studied. There has been much comment on the figures present- ed in the table and the report which must be seen as being representative of a mature technology. Beet has not been grown on a large scale in New Zealand and hence the data is less reliable than for say, pasture. It certainly seems that the yield of beet quoted in the report is too high for the present level of understanding of commercial beet growing in New Zealand. The costs in 1979 are significantly higher than the 1977 costs given in the report. Any arguments about growing beet or other crops for energy can only be resolved by large-scale trials and commercial growing on a substantial scale. Of particular importance is the yield of fermentable sugars and the storage qualities of beet in the ground and in stock piles under various climatic con- ditions.
Table 2. Energy Ratios and Production Costs for Agricultural Crops
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Forestry
Radiata pine is a resource which could be used for energy farming. Current planting rates exceed 40 000 hectares per year and the total exotic forest area exceeds 700 000 hectares. While the existing mature forest is almost entirely committed to providing feedstock for existing processing plants and for export and domestic demand, the fate of the forest now being planted has by no means been determined.
Thus in the early 1990s a considerable quantity of wood could become available for energy farming. A decision at the present time to implement energy farms based on forest crops would mean that such crops probably could not be available until well into the 1990s because of the growing time required for any species.
The energy ratios and production costs for radiata pine are given in Tables 3 and 4. Two different forest planting schemes have been considered:
(a) energy forest 18 year rotation;
(b) conventional forest 30 year rotation.
It should be noted that for both forest and agricultural crops, the opportunity costs are included in the production cost and that for agricultural crops this is a major proportion of the total cost while for radiata pine it is small.
The energy ratios for radiata pine are high showing that there is an adequate energy return. Transport is an important item — the processing plant should be sited close to the forest (or a beet processing plant).
Studies have been made of the use of forest residues and wood wastes, but it is not possible to obtain sufficient quantities of these to manufacture large amounts of liquid fuels. It is acknowledged, however, that these may well be the feedstock of the first processing plants because they are much cheaper than whole tree feedstock.
Table 3. Energy Ratio for Radiata Pine
Ratios in parentheses are ratios of output to input. Other figures in parentheses are percentages of total.
Percentages may not add because of rounding.
Table 4. Production Costs for Forestry
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Other Species
A wide variety of other species has been suggested but by and large there is inadequate data to adequately evaluate any of them. Any alternative crop would need to be significantly better in terms of yield and cost of production than 'con- ventional' crops in order to succeed at least in the initial period. Eventually a dif- ferent energy crop could well become important.
Processing to Transport Fuel
The following process routes have been considered:
Beet to ethanol Forage to ethanol and methane Wood to ethanol Wood to methane
Maize to ethanol Wood to hydrogen Forage to methane Wood to methanol
There are basically two processing routes which can be used to transform the biomass into a fuel for use in vehicles. The first of these, fermentation, is biological in character and operates at normal temperatures and pressures. The study has shown that small-scale plants processing feedstock at the rate of 200 to 1000 oven dried tonnes per day could be economic. There is considerable experience in New Zealand on fermentation plants of various types (e.g. brewing, wine-making, sewage treatment) so that they may well be favoured in the initial stages of any energy farm- ing program. This study has shown, however, that the fermentation plants, to be economic, require crops from highly productive land in New Zealand, some of which is currently used for intensive cropping and livestock production.
The second processing route is gasification which uses high temperatures and pressures. The gasification routes tend to be economic at a larger scale, i.e. from 500 oven dried tonnes of feedstock per day to 2500 oven dried tonnes (ODt) per day.
There is little experience in New Zealand with this type of plant and indeed it is the subject of much overseas research and development. It does, however, have the advantage over fermentation plants in that it should operate well using a woody feedstock such as radiata pine, straw residue or gorse and hence an energy farming process using this route would either use land which is not of great value for other more intensive activities or in the case of straw residues, use a feedstock with little alternative use.
In Table 5 the costs of fuel produced for some of the various routes studied are presented. The cost of feedstock is shown, together with the proportion it represents of the total cost. In all cases this is a high proportion. It should be noted that since the energy ratios are high (Tables 2 and 3) cost is by far the most important criterion;
so if energy farming is to succeed, the cost must be low enough. The December 1978 cost of gasoline is also given, and it will be noted that for the best routes the cost of ethanol or methanol is not greatly above that cost.
The processing of forest products in New Zealand is conventionally through a highly integrated forest-industrial system. For conventional agricultural products the degree of integration is considerably less. For energy farming it would be essen- tial to develop a fully integrated agro-industrial system for efficient production of transport fuel. The cost of transporting feedstock to the processing plant is a sig- nificant proportion of the cost of production. There are economies of scale in the various process routes, e.g. a large gasification plant processing 2500 ODt of wood per day is more economic than a 1000 ODt per day plant. However, a larger pro- cessing plant intake means a larger area of land which is required to supply the plant and hence a larger and more costly feedstock collection system. When feasibility 96
studies for plants in particular regions are undertaken, there will be a need to strike a careful balance between land suitability and availability, transport distance in- cluding relation of the transport network to land availability, and processing plant size and location.
Environmental and Social Factors
In all of the above studies, environmental factors have been considered. For instance, allowance is made in design of the processing plants to recycle the waste materials to farms where this is appropriate. Cropping systems have been designed to interfere as little as possible with the existing farm environment and for most, the use of fertiliser has been minimised.
A small survey of the maize industry in the Waikato was undertaken. This shows that a diversification into an energy farming crop will have its main effect at the farm level, with other consequences likely as repercussions run out from that point.
There is, however, some uncertainty as to the degree of the effects on farmer/farm operations and beyond until further details on the energy farming operations are known. Farmers and people associated with the farming industry are very receptive to the idea of energy farming but it is apparent that some additional incentive may be required in the initial phases. This will be sensitive to the scale of operation in the locality.
Table 5. Cost of Transport Fuel
Notes: 1. Gasoline cost is December 1978 2. Other costs are June 1977
3. Costs are quoted in c/L of gasoline equivalent, i.e. since alcohols burn more efficiently in engines, a lower amount of energy is required for the same distance travelled when compared with gasoline.
On-going Program
Over the next fifteen years New Zealand is likely to invest substantial amounts of capital and other resources in the manufacture of liquid fuels from Maui natural gas. The transport fuels so produced are likely to be cheaper than comparable fuels using biomass feedstock. However, there are many advantages to be gained by undertaking a complementary energy farming program at a modest level to test the 97
biomass production and processing technology, and to set the scene for rapid imple- mentation of this option when required.
The report recommends a program with the following two principal objectives:
(a) to have a single 200 ODt per day of feedstock fermentation ethanol plant on line by 1982;
(b) to have a single 500 ODt per day of wood gasification methanol plant on line by 1988.
Only two commercial plants are envisaged in this on-going program but if these objectives were achieved, New Zealand would be well positioned to proceed rapidly with a major energy farming program, should the economic and social climate of the late 1980s require it. To facilitate future rapid implementation a necessary adjunct would be a substantial research, development and demonstration program to obtain the required knowledge and experience. It would also be a prerequisite that this knowledge and experience be locally and readily available throughout New Zealand.
This concept has received widespread support and the Government has already obtained expressions of interest from a number of companies interested in the con- struction of the 200 ODt per day ethanol plant based on agricultural crops. At least one group is already committed to a full scale feasibility study. While there is a diversity of opinion within the Government as to the desirability of constructing such a large plant, any opposition is likely to disappear if such a plant is built with- out or with only minimal Government subsidy. The Minister of Energy is an en- thusiastic supporter of the idea of taking energy farming to a commercial scale.
Farmers too see considerable merit in going to a major plant at this stage.
Time is needed to research and to fully prove variations in the technology and to solve some of the problems (e.g. waste disposal) connected with energy farming. For instance the development of new crop species especially suitable for energy farming may take many years. New Zealand's crops, climate, farming and forestry differ from those in other parts of the world and the solution for this country will be unique. Only if money is invested now in the on-going program can the longer-term elements of the program be brought to a timely conclusion.
The report makes general recommendations on the on-going research program and these have by and large been accepted by the research community. There is now a difficult task of formulating the precise research projects and obtaining funds.
Reviewers have made many suggestions about individual research projects. Tech- nological manpower in New Zealand is a scarce resource and we need to make some bold decisions if our scientists and engineers are to be used in the most productive fashion in energy farming research.
Review of Report
'The Potential of Energy Farming for Transport Fuels in N . Z . ' (NZERDC Report No 46) was formally reviewed at a two-day workshop on 22 and 23 November 1979 and a seminar on 30 November 1979 attended by over 100 people from research establishments, industry, government and the farming community. A public meet- ing at Lincoln College was attended by 100 people including key figures in the farm- ing hierarchy.
Submissions from individuals amount to over 250 pages of material much of which is valuable commentary on the report including discussion of issues which were beyond the competence or frame of reference of the original study group.
The results of this review process are now being collated and will result in a third volume of the report in early 1980.
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