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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

Situation on the Bloemfontein Campus, and letter to parents
2016-02-28

Letter to parents from Prof Jonathan Jansen, Vice-Chancellor and Rector of the UFS 

 

Statement by Prof Jonathan Jansen, Vice-Chancellor and Rector of the University of the Free State (UFS) about the situation on the Bloemfontein Campus


1.    As all of you know, last night we witnessed a really tragic event at Xerox Shimla Park on the Bloemfontein Campus on the occasion of the Varsity Cup rugby match between NMMU (FNB Madibaz) and UFS (FNB Shimlas).
2.    The game started at 18:30 and about 17 minutes into the match, a group of protestors sitting on the north-eastern side of the stadium decided to invade the pitch and disrupt the game in progress.
3.    After a short while, some of the spectators also invaded the field, chasing and brutally beating those protestors whom they caught.
4.    As a university leadership we condemn in the strongest terms possible the vicious attack on the protestors. Nobody, repeat nobody, has the right to take the law into their own hands. While the protests were illegal and disruptive, it did not harm to the physical well-being of the spectators.
5.    The reaction from the group of spectators, however, not only opened old wounds, it trampled, literally and figuratively, on the dignity and humanity of other human beings. This we condemn in no uncertain terms, and no stone will be left unturned to find those who acted so violently on what should have been a beautiful occasion that also brought families and young children together to enjoy an evening of sport.
6.    I cannot over-emphasise our level of disgust and dismay at the behaviour of the spectators. It is NOT what the University of the Free State (UFS) is about and we are working around the clock to gather evidence on the basis of which we will pursue both charges and, in the case of students, also disciplinary action on campus.
7.    At the same time, the invasion of the pitch is also completely unacceptable and we will seek evidence on the basis of which we will act against those who decided to disrupt an official university event.
8.    Clashes between students occurred afterwards on campus and members of the Public Order Policing had to disperse some of them. The situation was stabilised in the early hours of the morning.
9.    Disruption continued this morning (23 February 2016) when students damaged some university buildings, a statue, and broke windows. Additional reinforcements from the South African Police Service were brought in to stabilise the campus. Additional security has also been deployed.


Broader picture
10.    We are very aware of the national crisis on university campuses and the instability currently underway. While the UFS has been largely peaceful, we have not been spared this turmoil, as last night’s events showed.
11.    We are also conscious of the fact that even as we speak, various political formations are vying for position inside the turmoil in this important election year. In fact, part of the difficulty of resolving competing demands is that they come from different political quarters, and change all the time.
12.    We are therefore learning from reliable sources that the Varsity Cup competition is, in fact, a target of national protests in front of a television audience.
13.    And we are aware of the fact that these protests are not only led by students but also by people from outside who have no association with the university. Just as the violent spectators involved on Monday night also included people from outside the university.

The demands

14.    My team has worked around the clock to try to meet the demands of contract workers demanding to be in-sourced. In fact, this weekend past, senior colleagues sat with worker leaders in the township to try to find ways of meeting their demands. We were hoping that such an agreement would be finalised by Monday afternoon (22 February 2016), but on the same Monday morning workers and students were arrested after moving onto Nelson Mandela Avenue, after which the South African Police Service (SAPS) took over as the matter became a public safety concern outside the hands of the university. Since then, it was difficult to return the workers to settle on a possible agreement.
15.    The fact is that the UFS has been in constant negotiation with contract workers to provide our colleagues with a decent wage and certain benefits. In fact, towards the end of last year we raised the minimum wage from R2 500 to R5 000. We were in fact hoping that the continued negotiations would improve that level of compensation even as we looked at a possible plan for insourcing in the future. We made it clear that if we could insource immediately, we would, but that the financial risk to the university was so great that it threatened the jobs of all our staff. Those negotiations were going well, until recently, when without notice the workers broke away and decided to protest on and around campus.
16.    While these negotiations were going on, the Student Representative Council (SRC) on Monday 22 February 2016 also decided to protest. While the vast majority of our 32 000 students were in classes and determined to get an education, a very small group led by the SRC President decided to protest; some invaded the UFS Sasol Library and the computer centre, and with the President eventually made their way to Xerox Shimla Park on which route they confronted the police, interrupted traffic and in fact injured some of our security staff as well as police officials.
17.    The university is definitely proceeding to collect evidence on these illegal and violent acts and will also act firmly against students involved in these protests.

Summary
18.    The events of Monday night represent a major setback for the transformation process at the UFS. While we have made major progress in recent years—from residence integration to a more inclusive language policy to a core curriculum to very successful ‘leadership for change’ interventions for student leaders—we still have a long way to go.
19.    One violent incident on a rugby field and we again see the long road ahead yet to be travelled. As I have often said before, you cannot deeply transform a century-old university and its community overnight. We acknowledge the progress but also the still long and difficult path ahead. We will not give up.
20.    We have 32 000 students on our campuses; the overwhelming majority of them are decent and committed to building bridges over old divides as we have seen over and over again. So many of our students, black and white, have become close and even intimate friends working hard to make this a better campus and ours a better community and country. Like all of us, they are gutted by what they saw on Monday, but the hundreds of messages I received from parents, students, and alumni this past 20 hours or so said one thing—keep on keeping on. And we will.

 

The Big Read: An assault on transformation (Times Live kolom deur Prof Jonathan Jansen: 25 Februarie 2016)

 

 

 


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