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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

Position statement: Recent reporting in newspapers
2014-10-03

 

You may have read reports in two Afrikaans newspapers, regarding recent events at the University of the Free State (UFS). Sadly, those reports are inaccurate, one-sided, exaggerated and based not on facts, but on rumour, gossip and unusually personal attacks on members of the university management.

Anyone who spends 10 minutes on our Bloemfontein Campus would wonder what the so-called ‘crisis’ is about.

We are left with no choice other than to consider legal action, as well as the intervention of the South African Press Ombudsman, among other steps, to protect the good name of the institution and the reputation of its staff. No journalist has the right to launch personal and damaging attacks on a university and its personnel, whatever his or her motives, without being fair and factual. In this respect, the newspapers have a case to answer.

But here are the facts in relation to the reports:

  1. No staff member, whether junior or senior, is ever suspended without hard evidence in hand. Such actions are rare, and when done, are preceded by careful reviews of our Human Resource Policies, labour legislation and both internal and external legal advice. Then, and only then, is a suspension affected. A suspension, moreover, does not mean you are guilty and is a precautionary action to allow for the disciplinary investigation and process to be conducted, especially where there is a serious case to answer.
  2. At no stage was the Registrar instructed to leave the university; this is patently false and yet reported as fact. We specifically responded to the media that the Registrar does outstanding work for the university and that it is our intention for him to remain as our Registrar through the end of his contract in 2016.
  3. The Rector does not make decisions by himself. Senior persons, from the position of Dean, upwards, are appointed by statutory and other senior committees of the university and finally approved by Council. No rector can override the decision of a senior committee, and this has not happened at the UFS even in cases where the Rector serves as Chair of that committee. The impression of heavy-handed management at the top insults all our committee structures, including the Institutional Forum – the widest and most inclusive of stakeholder bodies at a university – which reports directly to Council on fairness and compliance of selection processes.
  4. In the case of senior appointments, Council makes the final decision. Council fully supports the actions taken on senior appointments, including a recent senior suspension. The fact that one Council member resigns just before the end of his term, whatever the real reason for this action, does not deter from the fact that the full Council in its last sitting approved the major staffing decisions brought before it. The image therefore that the two newspapers try to create of great turmoil and distress at the university, is completely unfounded.

Even if we wanted to, the university obviously cannot provide details about staffing decisions, especially disciplinary actions in process, since the rights of individuals should be protected in terms of the Human Resource Policies and procedures of the UFS. But that does not give any newspaper the right to speculate or state as fact that which is based on rumour or gossip, or to slander senior personnel of the university. For these reasons, we have been forced to seek legal remedy and correction as a matter of urgency.

Make no mistake, underlying much of the criticism of the university has been a distress about transformation at the UFS; in particular, the perception is created that white colleagues are losing their jobs. The evidence points in the opposite direction. Our progress with equity has been slow and we lag far behind most of the former white universities; that is a fact. More than 90% of our professors are white; most of our senior appointments at professorial level and as heads of department are still overwhelmingly white. Reasonable South Africans would agree that our transformation still has a long way to go and only the mean-spirited would contend otherwise. But based on the two Afrikaans newspaper reports, an impression is left of the aggressive rooting out of white colleagues.

In the past few years the academic standard of the university has significantly improved. We now have the highest academic pass rates in years, in part because we raised the academic standards for admission four years ago. We now have the highest rate of research publications, and among the highest national publication rate of scholarly books, in the history of the UFS. We have one of the most stable financial situations of any university in South Africa, with a strong balance sheet and growing financial reserves way beyond what we had before. We now attract top professors from around the country and other parts of the world, and we have the highest number of rated researchers, through the National Research Foundation, than ever before. And after the constant turmoil of a number of years ago, we now have one of the most stable campuses in South Africa. Those are the facts.

The UFS is also regarded around the world as a university that has become a model of transformation and reconciliation in the student body. The elections of our Student Representative Council are only the most visible example of how far we have come in our leadership diversity. Not a week goes by in which other universities, nationally and abroad, do not come to Kovsies to consult with us on how they can learn from us and deepen their own transformations, especially among students.

Rather than focus on what more than one senior journalist, in reference to the article in Rapport of 21 September 2014, rightly called ‘a hatchet job’ on persons and the university, here are the objective findings of a recent survey of UFS stakeholders: 92% endorse our values; 77% agree with our transformation; 78% believe we are inclusive; and 78% applaud our overall reputation index.  Those are very different numbers from a few years ago when the institution was in crisis.

This is our commitment to all our stakeholders: we will continue our model of inclusive transformation which provides opportunities for study and for employment for all South Africans, including international students and colleagues. We remain committed to our parallel-medium instruction in which Afrikaans remains a language of instruction; we are in fact the only medical school in the country that offers dual education and training in both Afrikaans and English for our students - not only English. We provide bursaries and overseas study opportunities to all our students, irrespective of race. And our ‘future professors’ programme is richly diverse as we seek the academic stars of the future.

We are not perfect as a university management or community. Where we make mistakes, we acknowledge them and try to do better the next time round. But we remain steadfast in our goal of making the UFS a top world university in its academic ambitions and its human commitments.

END

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