CFC Project Proposal
Over the past 10 years, research in Europe, USA, Australia and Africa has highlighted the potential of using sweet sorghum as a feedstock for ethanol, heat and electricity production- so-called Combined Heat & Power (CHP). In Africa (Zimbabwe), this research was based on the concept of using sweet sorghum to supplement existing Zimbabwean fuel ethanol and electricity production from sugarcane molasses and bagasse (see Scurlock et. al. 1991). To date, research has concentrated on the agronomy of sorghum growth ie. produce new varieties with higher levels of biomass production, sugars and fibre. This concept of integrating sweet sorghum with sugarcane to produce ethanol and electricity is novel, and indeed, to our knowledge a commercial-scale sorghum ethanol system has not yet been demonstrated. As a result of the success of this agronomic research it now makes sense to demonstrate the potential for sweet sorghum as an energy crop at the commercial scale for the reasons discussed below.
Sweet sorghum can be grown in a co-cropping system where idle, fallow sugarcane land is used to produce sweet sorghum, which is then harvested before the sugarcane would normally be replanted. The availability of fallow sugarcane land is limited due to sugarcane's ability to ratoon (vigourous regrowth of new sugarcane shoots from existing root stock is possible for 10 or more years without the need to replant after harvesting), however, significant quantities of fallow land are still available. (see section G) As shown below the potential benefits of such a sorghum to energy 'add-on' system are: vertical diversification; broadening the income base for smallholder sugarcane producers; greater use of capital equipment (both agronomic and mill-based); reduced dependency on imported energy- both within the mill and nationally; better use of resources, especially labour and water; and a range of environmental benefits and longer production seasons.
The current global market for fuel and potable alcohol is strong and expanding, as a result of which ethanol production from sugarcane and sugarbeet molasses is increasing. Ethanol is now used as a automotive fuel and octane enhancer (fuel oxygenate) in Brazil, the United States and several countries in the European Union, where its environmental benefits are well recognised. This large scale ethanol production is derived from sugarcane, maize, and sugarbeet and significant improvements to the efficiency of this production are possible. Sweet Sorghum has never been used for commercial fuel ethanol and electricity production, despite its rapid growth rate and high yields and its highly efficient use of resources, e.g. water and nutrients. These characteristics should make sorghum a valuable resource for the future.
With sugarcane-based sugar production, it is currently more profitable to extract the maximum amount of crystalline sugar which has greater market value than ethanol after fermentation. The extraction of most of the sugar directly reduces the residual sugar levels in the final molasses sent to the fermentation plant thereby reducing ethanol production. Sweet sorghum grown on fallow sugarcane land would not impact on sugarcane growth, but could provide significant amounts of sugars. However, the extracted juice from sweet sorghum stems is not only rich in sugars, but also aconitic acid which makes crystallising the sucrose in a pure form technically difficult. It is therefore better to ferment sweet sorghum juice directly to produce ethanol than to extract crystalline sugar first and then ferment the molasses.
A key aspect of this project will be to maximise economic viability by deriving the optimal utilisation of equipment, land and resources, through the careful integration of sweet sorghum production with sugarcane production. The project will therefore assess the feasibility of increasing ethanol and electricity production utilising idle land and equipment without impacting on sugar production. The logistics of integrating two crops in this way is complex, and is sensitive to climate, soil, technology and management, therefore, practical tools which aid decision making will prove important, and will be developed within this project. The economics of ethanol production from sweet sorghum are strongly dependent on achieving high yields of both total biomass and sugars from sweet sorghum, and therefore research to date has concentrated on developing varieties with the correct agronomic characteristics.
In order to realise the undoubted potential of Sweet Sorghum for energy production as a commercially viable system it is now necessary to demonstrate a sorghum to ethanol and electricity system within an existing facility. Triangle Ltd. Zimbabwe, represents an ideal facility for this proposed demonstration project as it has excess ethanol production capacity, and sufficient fallow sugarcane land. Triangle Ltd. has been running a 40 Ml per year ethanol fermentation plant for the production of fuel alcohol (Ethanol) for the last 16 years to supply the internal gasoline market with blended fuel. This plant was originally constructed to address problems of energy security with economic considerations of secondary importance. To increase revenue, Triangle Ltd. has reconfigured it's plant to maximise crystalline sugar production from sugarcane at the expense of ethanol production. However, there is also a strong international market for ethanol mainly driven by environmental requirements of ethanol as a fuel oxygenate in the United States and Europe and as a petroleum substitute in Brazil. (see attachment 2) That sweet sorghum could provide a supplementary ethanol production feedstock for Triangle has been shown through agronomic trails on 0.5 hectare plots in Zimbabwe undertaken by the Biomass User's Network - Zimbabwe (BUN-Zim) in collaboration with King's College London. The trials have shown that sweet sorghum can produce sufficiently high yields of sugars and fibre and that it has appropriate growth characteristics to be considered for large scale ethanol and electricity production.
Furthermore, whilst a biomass energy project may be successful in one location, problems can be encountered when replicating such a project in another location. Historically, policy makers and entrepreneurs have sometimes failed to recognise the complexities involved with bioenergy schemes which are often critically dependant on site specific factors, and the introduction of new technologies may have unforseen knock-on effects. Therefore, in conjunction with the agronomic trials and agroindustrial demonstration, user friendly decision support tools will be developed to enable replication and understand the impacts of novel technologies at other potential sites. King's College London is currently developing a computer based systems analysis model (AIP-Agrosystems Integration Package) for the integration of sweet sorghum with sugarcane (see Attachment 6). As this integration has not been demonstrated before, the proposed demonstration project will provide an invaluable reference and data on the impacts and potential benefits of such a system. The decision making tools (AIP) will allow economic and technical decisions to be made on the viability of sorghum systems, including the potential impact of advanced conversion technologies and crop varieties, in Zimbabwe and other countries in Southern Africa, and indeed globally.
In summary, this project will demonstrate:
1) Techno-economic viability- including resource requirements and environmental impacts.
2) That sweet sorghum is agronomically suitable of being grown without disrupting current sugarcane agronomic schedules;
3) That existing sugarcane processing facilities are physically capable of processing sweet sorghum for the production of electricity and ethanol.
4) The development and validation of a modular computer model, capable of assessing the impacts of the use of different agronomic, industrial and technical variables on the entire energy and sugar production system- a decision support system for replication to other sites.
The project will be implemented in two phases. Phase I (Agronomy, years 1 & 2) centres on the selection of appropriate sweet sorghum varieties, planting and management regimes to ensure the appropriate quality and quantity of biomass will be available for ethanol heat and electricity production for Phase II. Phase II (demonstration and dissemination) will be carried out during year 3, after the mid-term assessment at the end of year 2. In Phase II sufficient sweet sorghum biomass (300 ha) will be produced for crushing and conversion to ethanol, heat and electricity utilising the Triangle Ltd's mill and equipment. Phase II will only be implemented after the successful completion of phase I, as assessed by the mid-term review. The systems analysis model will be developed in conjunction with both Phase I and II.
In a project of this nature it is essential that the different partner organisations work effectively together. The Zimbabwean PEA is the recently established Government-Industrial organisation SIRDC, and the director, Prof. Chetsanga, is the scientific advisor to the Government. SIRDC is therefore ideally placed to establish and co-ordinate this project. Additional information concerning SIRDC is provided in attachment 3. King's College London, in close collaboration with the Biomass User's Network- Zimbabwe has carried out a series of highly successful sweet sorghum trials in southern Zimbabwe, and has remained in close contact with Triangle Ltd in order to follow the successful sugarcane ethanol production programme from its inception.
Finally, this research and demonstration project will provide the data and expertise to conduct an
international workshop detailing the agronomic, technical, environmental and economic feasibility
of commercial scale Sorghum to energy systems. Dissemination and technology transfer will be
further aided through regular site visits by technicians / agronomists from other southern African
countries. Suitable donors and extension agencies will be identified and informed of the results,
and an international workshop will be conducted.
This project will broaden the sources of earnings to sugar producers and improve the long term profitability of the sugarcane industry in developing countries, but initially in Southern Africa - the focus region for this project. Broadening sources of income to sugar producers was identified as a key priority in the Sugar Development Strategy. (see attachment 1)
B. Wider (policy) objective:
(a) More cost effective use of water resources;
(b) More efficient use of land and labour; and
(c) Diversify production from sugar alone: sugar, alcohol, heat, electricity, and utilise residues such as trash for mulch and energy, i.e. broaden the income base.
(a) Increases biomass production per unit of land area;
(b) More efficient use of machinery and land; the crushing season can be expanded by one or more months;
(c) Extending the harvesting and milling season will improve efficiency of land and water use; and
(d) Better utilises available ethanol and electricity production capacity.
(a) Increase the use and availability of renewable energy;
(b) Reduction of vehicle emissions if alcohol used for fuel;
(c) Local source of energy (ethanol, heat, electricity and bio-gas);
(d) Carbon neutral energy sources with positive implications for global warming;
(e) Reductions in emissions of SOx and possibly NOx as a result of displacing coal with sorghum bagasse for the production of electricity and process energy;
(f) On-field stillage and ash recycling which will result in increased yields and decreased fertilizer inputs; and
(g) Controlling nitrate run-off from farmland if sweet sorghum is used as a buffer between
sugarcane and water courses by utilising sorghum's ability to extract soil nitrogen efficiently.
(iv) Social Objectives
(a) Extending the harvesting and milling season will reduce the seasonality of employment in field and factory;
(b) Broadening of skills level in the regional workforce; and
(c) Increases in rural income by providing an extra cash crop (sweet sorghum) for small scale commercial and communal farmers who would provide the main feedstock for expansion of ethanol and electricity production from Sweet Sorghum.
C. Immediate objectives:
By mid-1999 to:
i) Demonstrate the feasibility of co-cropping sweet sorghum with sugar cane on two test sites in Zimbabwe, through agronomic trials and biomass production;
ii) Demonstrate the economic and technical viability of utilising sweet sorghum within an existing sugar mill for energy production by using the existing mill land and facilities for electricity, heat, power and ethanol production;
iii) Development of a systems analysis model and decision support system to assess the replicability of the co-cropping system and the impacts of novel technologies ie. allow the impact of novel technologies and management practices to be assessed throughout a complete energy chain in order to minimise economic and technical risk;
iv) Disseminate the project outputs and facilitate technology transfer.
This demonstration project will provide the basis for future extension once it has demonstrated the agronomic, technical, economic and environmental feasibility of commercial scale sorghum to ethanol and electricity systems.
(a) Zimbabwe as site for project;
(b) Kenya, Malawi, Mozambique, Tanzania, and Zambia through information dissemination and exchange visits to Zimbabwe site by technicians / agronomists to facilitate technology transfer; and
(c) All cane producing members of ISO and CFC when the detailed, analytical documentation is distributed free at the end of the project- members are also invited to attend workshop.
(ii) Population Groups
(a) Rural workers;
(b) Factory workers;
(c) Communal farmers;
(d) Commercial cane growers; and
(e) The broader population through a lower than otherwise level of polluting emissions when
ethanol produced from sweet sorghum is used as a fuel oxygenate.
Justification of the project's wider objectives
E. Conformity of objectives with the policies of the Common Fund:
As demonstrated in the project objectives this project clearly meets CFC objectives and priorities including:
(a) Research and development;
(b) Productivity improvement;
(c) Vertical diversification; and
(d) Improvement of resource management.
(e) A technical exchange programme enables technicians and agronomists from 5 other southern African countries with significant sugarcane industries to participate.
The contribution of the project to the ISO's Sugar Development Strategy is explained in
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