Written by Henry Neondo
A study led by researchers from icipe and its partners has demonstrated the superiority of solar concentrating technology. Dr. Wilber Lwande, icipe scientist says the findings of the research, which was funded by the Critical Ecosystem Partnership Fund (CEPF) and the Swiss-based Biovision Foundation, present a major breakthrough towards unlocking the full commercial potential of A. secundiflora, a succulent perennial herb that is one of about 450 species of the genus Aloe.
“The A. secundiflora species, which is found in the arid and semi-arid regions in Kenya, southern Ethiopia, Rwanda and Tanzania, is a significant source of livelihood for marginalised communities. Indeed, based on its potential in that regard, various programmes have been initiated by a variety of organisations to promote the cultivation and processing of A. secundiflora. For instance, in Kenya, the Kenya Wildlife Service (KWS), has established regulations and developed a long term strategy for the sustainable exploitation of Aloe species,” explains Dr. Lwande.
He, however, observes that the unsustainable and environmentally destructive methods currently used in the processing of A. secundiflora pose a major draw-back in its exploitation.
The main source of the commercial value of A. secundiflora, Dr Lwande explains, is a yellow bitter sap paste, which is used in the manufacture of pharmaceutical and cosmetic products and in alcoholic beverages. Local communities cut the leaves of the plant at the base and drain the sap, which they then sell to dealers who process it into a rock-hard dark green paste, primarily for export.
“The sap from the leaves of A. secundiflora has a high percentage of water, which has to be removed to form a stable paste. Local dealers process the sap into paste by heating it in drums mounted on traditional three-stone fuelwood cooking stoves. The icipe-led study found that this processing method utilises approximately 4.1 tonnes (4,100 kilogrammes) of fuelwood to process one tonne of paste,” notes Dr Lwande.
Given that about 11 tonnes of A. secundiflora paste is produced annually in Kenya, its processing therefore consumes an estimated 45 tonnes of fuelwood, which is sourced from the meager vegetation resources in the semi-arid areas. Such large quantities of fuelwood not only contribute to deforestation and loss of biodiversity but also to carbon dioxide green house gas emissions, whose long term effects include environmental and land degradation and climate change respectively, observes Dr Lwande.
However, the icipe-led researchers found that the required temperature range of 90 to 100o centigrades is easily attainable using solar cookers, utilising solar energy that is free and abundant, especially in the semi-arid and arid areas of Africa where A. secundiflora grows, Dr Lwande further explains.
The researchers also established that the paste obtained from A. secundiflora sap using solar concentrating technology was more stable and of higher quality and value. For instance, the paste had a higher content of Aloin A, compared to that produced using either electricity or fuelwood.
Aloin A (or Barbaloin) is an anthraquinone glycoside, a bitter, yellow-brown coloured compound found in the exudates of Aloe species.
The compound is used as a stimulant laxative in treating constipation and as a bittering agent in commercial alcoholic beverages. Aloin content is generally used as a standard measure of the quality of Aloe extracts.
“The variations in Aloin content in A. secundiflora paste produced using solar, electricity and fuelwood energy could be attributed to possible changes in thermo-chemical reactions in the sap. For instance, the use of fuelwood could result in overheating, while solar energy provides a more gentle heating process. We also found solar energy to be more efficient in reducing the water content of A. secundiflora leaf sap as compared to electricity and fuelwood energy, thereby providing a more stable paste,” explains icipe scientist, Dr. Wilber Lwande.
“Based on the results of the study, we conclude that solar concentration technology is an attractive alternative to using fuelwood to process A. secundiflora leaf sap into paste. In the long term, the use of solar energy as a substitute for fuelwood energy would contribute to reduced deforestation, environmental degradation, global warming and climate change. It would also improve biodiversity conservation and reduce the burden on women and children associated with collecting and transporting fuelwood,” Dr Lwande said.