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The spineless cactus, a promising source of sustainable energy

15 May 2023 | Story Leonie Bolleurs | Photo Supplied

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

SRC Inauguration speech: 22 January 2005

2005-01-22

Campus Head (Prof Peter Mbati). Dean of Students (Dr Natie Luyt). Deputy Director: Student Affairs and my boss (Mr. Teboho Manchu), Members of the University executive and Academic staff members, SRC members, Leaders of trade Unions and Student organizations, Distinguished guests, Ladies and gentlemen, most importantly first entering students and Parents receive my heartfelt revolutionary greetings.

Let me extend my word of appreciation to our distinguished guests for adding value and dignity to this event. Your presence here means a lot to us. Program Director what I bring here with me, assisted by facts, and is therefore just the work of my imagination. Like a love letter addressed to a sweetheart miles away, even though you do not know how she feels, what she wants to hear, and do not even know how her face looks like.

To me a speech is just an honest and intimate conversation. That is why I got into the habit of establishing a dialogue, or a debate, with my acquaintances looking at their faces and trying to persuade them of what I am telling them.

Mr. Speaker and Madam Deputy Speaker of the Student Parliament we are gathering at this ceremony, significantly few weeks after the release of grade 12 results, with the exception of those from Mpumalanga because of fraud. The Grade 12 results also show that only 18% of Black learners matriculated with exemptions, as compared to 53, 6% of white learners. This is an indication that our education system needs an overhaul.

We are also gathered here significantly a day after the management retreat held in Bloemfontein, Masselspoort. The retreat discussed, among other things, the transformation agenda, and some possible solutions to challenges we are facing now.

Most regrettably, we are gathered here when the whole world morns the victims of Tsunami tragedy. Let me therefore tore the line and convey our deepest condolences, from the last robot of my heart, to the affected families. Our hearts and thoughts will always be occupied by this horrified tragedy.

Creating a new Institution

I would submit, for purposes of debate and discussions that this Institution should strive to specialize and excel in regional rural development studies. Since our higher education, institutions in South Africa are generally weak in rural development studies. Instead, most of them tend to have an urban orientation to their programmes. Training everybody for the cities, big business and the private sector. This is a big weakness in a country with such large rural areas and population trapped in poverty, disease and ignorance.

Women’s studies

Program Director, it is only a moron who can argue against the fact that for us to reposition the institution around the regional development challenge, we need to start first with women empowerment. It is a fact that in most of our poor communities and families, it is women who withstand the worst of poverty. They are the ones who daily have to wipe tears from children who are hungry. It is women who look after the sick, the elderly, those dying from AIDS and the jobless. They are the one who have to fetch water, make fire and cook. There can therefore be no rural development studies without women studies, in particular on how to empower them and assist in the provision of basic services, so that they are relieved from some of the burdensome task of the society.

Registration Process

Mr. Speaker and Madam Deputy Speaker of the Student Parliament let me indicate that the registration is a process and not an event, so it cannot be concluded overnight. This huge process demands for people to stay calm, as there is no crisis. People should stop being excited. At the same time, no organization should use its cheap popularity and unilaterally disrupt the continuous and smooth running of the registration process at hand.

Let me strongly indicate, madam deputy speaker, that I am on record for stating that I have forgiven all those who have wronged us. I harbour no bitterness towards the protagonists of our painful and unfortunate events of the past week. And we will overcome this process not by our own devices but by the help of Almighty God and the grace of our Lord Jesus Christ.

Concerning registration of first years, we have programs, concerning that of senior students, we have programs, regarding graduations we have programs, and concerning HIV\AIDS we have programs. So, there is no need for people to press panicking buttons.

Mr. Speaker and Madam Deputy Speaker of the Student Parliament let me be opportunistic and welcome the entire student body on Campus for the academic year 2005. May our lovely first entering students have a happy and momentous year as part of Qwaqwa Campus of University of the Free State. May your studies be fruitful and enjoyable.

Student years are generally the happiest years of your life, so please make the most of them. While you are doing, all your preparations bear in mind that University is not an opportunity, it is just creating opportunities for a person.

On behalf of SRC members, our people, our students and management members I would like to welcome you all. Even though your parents are far away, here at Uniqwa you have more brothers, more sisters and more parents. Since we will love you with the same love as if we are from one family, and I have no doubts that management members will love and care for you as if you are their own children. Should you encounter any problem while studying at the Qwaqwa Campus of University of the Free State do not hesitate to contact us at the SRC offices because we need to ameliorate any factor influencing you negatively while on campus. I wish you well in the attainment of your academic pursuit.

Senior Students: We are not faced with just a new year but another academic year where we all have to work together to achieve our common goal of building our Institution through the development of human power. I urge you to invest your whole selves in this SRC.

For quite some time now, a debate has been ranging as to, whether has there been any progress in this incorporation process, or we are just moving with no direction. This debate is important, but I hasten to add not essential. The SRC is also involved in this debate, but with definite shift in emphasis. For us it is not important to participate in the debate than it is in finding solutions for the challenges of this new chapter in the history of humankind.

To my colleagues: Comrades, we are leading this Institution with a sense of pride and duty, and I know very well that we lead men and women, students who are determined to ensure that we all reach our destination safely and on time.

I said in one of our meetings that there are more enemies on our way, more than we can imagine. I think you witnessed that during the course of this week. The excitement and unnecessary confusions caused by some confused and loosed charlatans bear testimony to my statements. We should not reveal our game plans unless we are ready to slam.

Let me also borrow from the words of the late Albert Lethuli when he said and I quote: “There remains before us the building of the new land, from the ruins of the old narrow groups, a synthesis of the rich cultural strains which we have inherited. The task is immense”. Lastly, a navy divided within its ranks will be vanquished and destroyed by the enemy, but a navy united in purpose and action, loyalty and commitment will not drawn but sail on to victory.

In conclusion, let me call upon all political structures, church denominations, developmental structures, clubs, societies and forums to put aside all their differences, ideological insinuations and forge unity towards transforming Qwaqwa Campus of University of the Free State into an institution that is seen playing vigilant role in developing students academically, politically, socially, spiritually, religiously, culturally and otherwise.

Program Director, let me end my speech by indicating that every drop of my blood is telling me that Uniqwa is my home. I firstly became a student here, I became an activist here, I became a leader here, I became a president here, I will become a graduant here and hopefully I will become an employee here. So never, doubt my commitment towards the community of this campus.

Please be informed, in a central University of Technology’s way, that if there is no UNIQWA in HEAVEN, then I am not GOING.

Let us broaden the social base.

Tello Titus Wa-Motloung President General

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