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15 May 2023 | Story Leonie Bolleurs | Photo Supplied
Spineless Cactus
Axel Tarrisse (far left), a PhD student in the Department of Sustainable Food Systems, working on the biogas and fodder potential of spineless cactus in Africa. Pictured with him are Prof Maryna de Wit, his supervisor and Associate Professor in the UFS Department of Sustainable Food Systems and Development, and Dr Herman Fouché from the Agricultural Research Council.

The spineless cactus is a unique perennial plant that is able to yield close to 40 tons of dry matter per hectare per year with a rainfall of 500 mm per annum. “This equates eight tons of biomethane or 11 000 litres of diesel-equivalent energy per hectare,” says Axel Tarrisse, a PhD student in the Department of Sustainable Food Systems and Development at the University of the Free State (UFS), who is working on the biogas and fodder potential of spineless cactus in Africa.

Tarrisse believes biogas, produced from the spineless cactus, has the potential to complement the supply of South Africa’s existing industrial energy companies to produce sustainable jet fuel and diesel and a variety of other products with the gas-to-liquid process they use.

Developing biogas

He says with rainfall, key nutrients, carbon dioxide, and solar energy it is possible to produce biomass from cactus.

“First, we harvest the cactus and macerate it prior to going into an anaerobic digester where it is heated to 38°C, the same as a cow’s body temperature. Inside the digester, naturally occurring bacteria, similar to those found in their stomachs, break down the cactus, resulting in the production of biogas. This biogas is composed of both methane and carbon dioxide,” he explains.

According to him, biogas generated through this process can be used in a number of ways. This includes running generators to produce electricity or burning it to generate heat. It will also serve as a feedstock to replace coal and natural gas used by companies such as PetroSA and Sasol in their production of synthetic renewable fuels.

“The methane can also be separated from the carbon dioxide and compressed into bottles, creating compressed biomethane. This can be used as a replacement for liquid petroleum gas (LPG), as well as petrol and diesel in vehicles, such as bakkies, tractors, buses, and delivery trucks.”

The carbon dioxide produced in the process can, for example, be used to replace the fossil-based carbon dioxide typically used in the production of carbonated beverages. Additionally, it can be applied to extend the shelf life of packaged foods, serve as a water softener, and even be applied to a variety of industrial applications.

Commercialisation 

Biogas/biomethane is already produced in Mexico on a commercial scale. In Northeast Brazil, farmers have planted 600 000 hectares of spineless cactus, also known as Palma Forrageira, but the machinery needed to harvest it only became commercially available this year.

Back home in South Africa, just 30 km outside of Bloemfontein, Barren Energy farm is at Stage 1 with 140 hectares of high-density cactus planted to provide the initial feedstock for anaerobic digestion. With 600 hectares, they will be able to produce five million litres of diesel-equivalent methane.

Tarrisse says, “With the right methodology and management system, producing biogas from the spineless cactus will be adopted relatively quickly on a commercial scale.”

He believes that the lack of investment in cultivating the spineless cactus as a crop for fodder in South Africa may be due to a few factors. “It is easier to stick to what is known, such as irrigating lucerne and maize and managing these crops with existing planters, pest management solutions, and harvesting machinery than to develop local machinery and management solutions for a perfectly adapted crop,” he says. 

Compelling reasons

According to Tarrisse, there are several compelling reasons to consider the spineless cactus as a source of biogas in South Africa.

Firstly, he explains, “Only the cactus pads, harvested from high-density plantations (20 000 plants per hectares), are used for biogas production.”

“Secondly, the spineless cactus can yield large volumes of biomass from marginal semi-arid land where conditions are unsuitable for conventional crop cultivation. This makes it an ideal option for the 65% of South African land that receives less than 500 mm of rainfall annually.”

Thirdly, he says, “The plant contains 30 to 50% of easily digestible sugars, which degrades easily in an anaerobic digester. This simple, low-tech process can provide a substantial amount of baseload energy with relatively limited capital expenditure, which is particularly important in developing countries such as South Africa where capital is difficult to raise.”

“On top of that, anaerobic digestion only extracts carbon, oxygen, and hydrogen molecules from the cactus, while most of the macro- and micronutrients, water, and some fibres remain in the digestate. This nutrient-rich cactus digestate can then be spread on the cactus fields, reducing the need for fertiliser once the plantation has been fertilised in the first two years of implementation.”

Societal impact

Besides the benefits of producing biogas from the cactus plant, there is also the opportunity of job creation. “This farming can create one million direct job opportunities from only 3% of South Africa’s land area, approximately 4 million hectares,” says Tarrisse.

He is of the opinion that if production was at scale, as opposed to the current small orchard-style farming of cactus, there would be substantial biomass available to sustain not only biomethane, but also to support various bio-industries, such as protein production through cactus fermentation, biomaterials as a substitute for wood-based cellulose, organic acids, and bioplastics. “Consequently, cactus provides a climate-resilient, drought-resistant, and perennial feedstock for food, feed, fibre, and fuel in semi-arid Southern Africa,” he says.

Tarrisse states that this initiative also has the potential to significantly reduce migration from rural to urban areas, therefore addressing issues related to the growth of urbanisation, such as the provision of infrastructure and crime.

News Archive

Gender bias still rife in African Universities
2007-08-03

 

 At the lecture were, from the left: Prof. Magda Fourie (Vice-Rector: Academic Planning), Prof. Amina Mama (Chair: Gender Studies, University of Cape Town), Prof. Engela Pretorius (Vice-Dean: Humanties) and Prof. Letticia Moja (Dean: Faculty of Health Sciences).
Photo: Stephen Collett

Gender bias still rife in African Universities

Women constitute about 30% of student enrolment in African universities, and only about 6% of African professors are women. This is according to the chairperson of Gender Studies at the University of Cape Town, Prof Amina Mama.

Prof Mama was delivering a lecture on the topic “Rethinking African Universities” as part of Women’s Day celebrations at the University of the Free State (UFS) today.

She says the gender profile suggests that the majority of the women who work in African universities are not academics and researchers, but rather the providers of secretarial, cleaning, catering, student welfare and other administrative and support services.

She said that African universities continue to display profound gender bias in their students and staffing profiles and, more significantly, are deeply inequitable in their institutional and intellectual cultures. She said women find it difficult to succeed at universities as they are imbued with patriarchal values and assumptions that affect all aspects of life and learning.

She said that even though African universities have never excluded women, enrolling them presents only the first hurdle in a much longer process.

“The research evidence suggests that once women have found their way into the universities, then gender differentiations continue to arise and to affect the experience and performance of women students in numerous ways. Even within single institutions disparities manifest across the levels of the hierarchy, within and across faculties and disciplines, within and between academic and administrative roles, across generations, and vary with class and social background, marital status, parental status, and probably many more factors besides these”, she said.

She lamented the fact that there is no field of study free of gender inequalities, particularly at postgraduate levels and in the higher ranks of academics. “Although more women study the arts, social sciences and humanities, few make it to professor and their research and creative output remains less”, she said.

Prof Mama said gender gaps as far as employment of women within African universities is concerned are generally wider than in student enrolment. She said although many women are employed in junior administrative and support capacities, there continues to be gross under-representation of women among senior administrative and academic staff. She said this disparity becomes more pronounced as one moves up the ranks.

“South African universities are ahead, but they are not as radically different as their policy rhetoric might suggest. A decade and a half after the end of apartheid only three of the 23 vice-chancellors in the country are women, and women fill fewer than 30% of the senior positions (Deans, Executive Directors and Deputy Vice-Chancellors)”, she said.

She made an observation that highly qualified women accept administrative positions as opposed to academic work, thus ensuring that men continue to dominate the ranks of those defined as ‘great thinkers’ or ‘accomplished researchers’.

“Perhaps women simply make realistic career choices, opting out of academic competition with male colleagues who they can easily perceive to be systematically advantaged, not only within the institution, but also on the personal and domestic fronts, which still see most African women holding the baby, literally and figuratively”, she said

She also touched on sexual harassment and abuse which she said appears to be a commonplace on African campuses. “In contexts where sexual transactions are a pervasive feature of academic life, women who do succeed are unlikely to be perceived as having done so on the basis of merit or hard work, and may be treated with derision and disbelief”, she said.

She, however, said in spite of broader patterns of gender and class inequality in universities, public higher education remains a main route to career advancement and mobility for women in Africa.

“Women’s constrained access has therefore posed a constraint to their pursuit of more equitable and just modes of political, economic and social development, not to mention freedom from direct oppression”, she said.

Prof Mama concluded by saying, “There is a widely held agreement that there is a need to rethink our universities and to ensure that they are transformed into institutions more compatible with the democratic and social justice agendas that are now leading Africa beyond the legacies of dictatorship, conflict and economic crisis, beyond the deep social divisions and inequalities that have characterised our history”.

She said rethinking universities means asking deeper questions about gender relations within them, and taking concerted and effective action to transform these privileged bastions of higher learning so that they can fulfil their pubic mandate and promise instead of lagging behind our steadily improving laws and policies.

Media Release
Issued by: Mangaliso Radebe
Assistant Director: Media Liaison
Tel: 051 401 2828
Cell: 078 460 3320
E-mail: radebemt.stg@ufs.ac.za  
02 August 2007
 

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