Integrating Sweet Sorghum and Sugarcane for Bioenergy: Modelling The Potential for Electricity and Ethanol Production in SE Zimbabwe

Research in to the use of sweet sorghum in Europe, Zimbabwe, and elsewhere is now based at Imperial College London (formerly at King's College London) and Themba Technology Ltd, and was co-ordinated by the late and sadly missed Prof. D.O. Hall. The research is led by Jeremy Woods located in the Division of Science & Technology at the College's South Kensington Campus.

This research is currently funded through the Common Fund for Commodities and previously by the European Union. It involves the collaboration between KCL, the Science and Industry Research and Development Centre (Zimbabwe), the Biomass User's Network (Zimbabwe), the DR&SS Lowveld Research Station (Zimbabwe), Triangle Ltd. (Zimbabwe), and the International Sugar Organisation (UK).

The progress of the research up to March 2000 is analysed in detail in Dr Woods' PhD thesis which is provided in full in Adobe Acrobat format below the Abstract.

Index and Chapter 1 (Uploaded 14-sep-01)

Chapter 2: Current Status (Uploaded 14-sep-01)

Chapter 3: Materials & Methods (Uploaded 14-sep-01)

Chapter 4: Results (Uploaded 14-sep-01)

Chapter 5: Discussion & Conclusions incl refs (Uploaded 14-sep-01)

Apendices (Uploaded 14-sep-01)

Sweet Sorghum Research Page

AIP Installation Files (VB 4 setup files)

Agrosystems Integration Package Install Files (7MB Zip file!) (Uploaded 14-sep-01)



ABSTRACT

 This thesis describes a new agriculturally-based bioenergy system which integrates sweet sorghum (Sorghum bicolor L. Moench), a rapid growth (3-5 months), C₄ sweet-stemmed annual crop, with the perennial crop sugarcane (Saccharum officinarum, 12-18 months growth period), to improve:

•   the length of the harvesting season

•   the efficiency of production of ethanol & electricity

•   the efficiency of use of land, water, equipment, personnel, & other resources

The research involved the development of a novel, prototype, systems-analysis model called the ‘Agrosystems Integration Package’ (AIP), which has been developed to:

•   assess the impact of integrating sweet sorghum with sugarcane at a specific site

•   optimise the selection of technologies to produce bioenergy (ethanol, electricity, and heat) from the sweet sorghum / sugarcane system


That such a novel bioenergy system can be integrated with existing sugarcane-based bioethanol systems is evaluated by using the Triangle Ltd. Sugarmill and sugarcane estates, located in the semi-arid region of southern Zimbabwe, as a model system.  The potential for co-cropping sweet sorghum with sugarcane was assessed both agronomically and in the agro-industrial conversion phase.  It was concluded that sweet sorghum could be grown for harvesting during the sugarcane ‘off-crop’ when the sugarmill and equipment is normally idle.  In addition, there is a good potential for year round processing and therefore biofuel production in an integrated sweet sorghum and sugarcane system.  The viability of the integrated system is dependent on maintaining high sugarcane yields and achieving sustainable and high sweet sorghum yields.  During this work sweet sorghum yields of over 70 tonnes above ground fresh biomass per hectare have been achieved for a single crop cycle at Triangle.

 Because sorghum is adapted to semi-arid areas and makes optimum use of scarce resources such as water and nutrients, its use should result in net improvements in the resource use efficiency for bioenergy production on sugar estates. In summary, this research has evaluated:

 i.            the site specific potential for bioenergy production from sweet sorghum

ii.             physical resource requirements, i.e.  water, nutrients and land

iii.            manpower needs, itemised by skill level

iv.            a basic economic evaluation

v.             energy, carbon, and nitrogen balances