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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

UFS awards degrees at autumn graduation ceremony

2009-04-28

The University of the Free State’s (UFS) autumn diploma and graduation ceremony took place this week in the Arena on the South Campus in Bloemfontein (formerly known as the Vista Campus). This arrangement has been made because of the large-scale renovations to the Callie Human Centre on the Main Campus.

Friday, 24 April 2009
Faculties of Health Sciences, Law and Theology Diploma ceremony

Law student’s achievement excels 80%
Four Law students obtained the LLB degree at this year’s autumn graduation ceremony of the University of the Free State (UFS) summa cum laude and were awarded the Moritz Bobbert Medal. They are from the left: Lezelle Olivier (80%), Albert Nell (91%) and Amanda du Toit (83%). LiFeng Chien were absent during the photo.

UFS awards degrees at autumn graduation ceremony
Today 331 students and five doctorates in the Faculties of Health Sciences, Law and Theology received their qualifications at this year’s autumn graduation ceremony of the University of the Free State (UFS). Michael Molahloe (left) and Mamokete Ntholeng both received their LL.B. degrees in the Faculty of Law.
Photo: Leonie Bolleurs

This year’s autumn graduation ceremony of the University of the Free State (UFS) was held on the South Campus. From the group of students that received their qualification from the Faculty of Law, is from the left: Janine Jonson, Anneska van der Spoel, Andrea Coetzer, and Jo-Mari Visser.
Photo: Leonie Bolleurs

Students in Nursing receive their degree
A group of students from the Faculty of Health Sciences received their B.Soc.Sc. degree at this year’s autumn graduation ceremony of the University of the Free State (UFS). At the occasion were, from the left: Ruth Beukes, Basetsana Panana, and Dipontsheng Tsolo.
Photo: Leonie Bolleurs

UFS Faculty of Health Sciences awards degrees
Liezl Swanepoel (left) and Heide van der Merwe received their BSocSC degrees at the University of the Free State’s (UFS) autumn graduation ceremony.
Photo: Leonie Bolleurs

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Thursday, 23 April 2009
Faculty of Natural and Agricultural Sciences & Chancellor’s Dinner

UFS awards unique doctorate
Dr Rodney Douglas, who had never obtained any formal undergraduate qualification, this week received a Ph.D. in Geography and Geology during the autumn graduation ceremony of the University of the Free State (UFS). The name of his thesis is “A new perspective on the geohydrological and surface processes controlling the depositional environment at the Florisbad archaeozoological site”. He had four papers published in journals that were related to his thesis. He obtained his South African Museums Association Diploma in Biology in 1988 and his M.Sc. in Environmental Biology at the University of Natal, Durban in 1992. He was accepted as a Master's degree student at that university based on research that he had conducted on, amongst others, the diets of reptiles. He has been working at the Department of Herpetology at the National Museum, Bloemfontein since 1984, where he holds the post of Principal Museum Scientist and Head of Department.
Photo: Leonie Bolleurs

Chancellor’s Dinner: UFS honours doctoral students
Last night, the University of the Free State (UFS) honoured students who had received their Ph.D. degrees at the autumn graduation ceremony this past week, at the Chancellor’s Dinner. A total of 25 doctorates were awarded during the respective ceremonies. Attending the occasion were, from the left: Dr Annemarie Kühn, Ph.D. in Chemistry, Prof. Jeanet Conradie, Department of Chemistry at the UFS and Dr Kühn’s promoter, Prof. Teuns Verschoor, Acting Rector of the UFS, Prof. Corene de Wet, Department of Comparative Education and Education Management at the UFS, and Dr Mafu Rakometsi, Chief Executive Officer of Umalusi and former head of the Free State Department of Education who received a Ph.D. in History. Prof. De Wet is Dr Rakometsi's co-promoter and the late Prof. Leo Barnard, former Head of the Department of History at the UFS, who passed away at the beginning of April 2009, was his promoter.
Photo: Leonie Bolleurs

Mrs Annemarie Kilian, Mr Willem Kilian (BSc. Hons) and Prof Stephanus Kilian
Photo: Mangaliso Radebe

Mr Jaco van der Merwe, Mr Renico Pretorius and Mr Rion Terblanche (all BSc. Quantity Survying)
Photo: Mangaliso Radebe

Ms Mamakoanyane Amelia Shata (BSc. Genetics and BSc. Hons. Plant Molecular Biology) and Mrs Maente Adelinah Shata.
Photo: Mangaliso Radebe

Mr Maurice Ambrose and Mr Owen Monk (both BSc. Quantity Survying).
Photo: Mangaliso Radebe

Ms Tobeka Mehlomekhulu (Lecturer: Department of Geography), Mr Neo Mokgosi (BSc. Hons. Genetics) and Ms Nwabisa Mehlomekhulu (BSc. Hons. Food Science).
Photo: Mangaliso Radebe

Mr John Mdane, Mr Fana Mdane (BSc. Information Technology) and Mrs Agnes Mdane
Photo: Mangaliso Radebe

Mr Kevin Vermaak (BSc. Hons. Geohydrology) and Ms Michelle Steenkamp (BSc. Hons. Geology).
Photo: Mangaliso Radebe

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21 April 2009
Faculty of Economic and Management Sciences

Prof. Magda Fourie's daughter graduates
Nadia Fourie, daughter of Prof. Magda Fourie, former Vice-Rector: Academic Planning at the UFS and now Vice-Rector: Teaching at Stellenbosch University, received the B.Com. Law degree.
Photo: Lacea Loader

724 degrees were awarded during the ceremony of the Faculty of Economic and Management Sciences. Here are, from the left: Simon Serutla, B.Com. Accounting, Lourencia Hamuaka, B.Com. Honours in Financial Economics and Investment Management, Sunet Opperman, B. Accounting, and Yolandi Greyling, B. Accounting.
Photo: Lacea Loader

Students in the Faculty of Economic and Management Sciences graduated this week during the University of the Free State's (UFS) autumn graduation ceremony. Altogether 724 degrees were conferred. Here are, from the left: Marie-Louise Lombard, B.Com. Law, Adriaan van der Merwe, B.Com. Law and member of the Student Representative Council (Legal and Constitutional Affairs), Basanio Ncike, B.Com. Economics, and Richard Schooling, B.Com. Banking.
Photo: Lacea Loader

Center for Accounting honours top achievers
The Centre for Accounting at the University of the Free State (UFS) honoured the top ten students in the third-year B.Com. and B.Com. Hons. programmes respectively during this week's autumn graduation ceremony. Here are, from the left: Prof. Ronell Britz, Chairperson of the centre, Nils Kotze, first place in the B.Com. third-year group, and Madri Victor, first place in the B.Com. Hons. group; back: Prof. Hentie van Wyk, Programme Director: Accountant Training.
Photo: Stephen Collett

Accounting firms in Free State help with recognition of top achievers
Accounting firms in the Free State have contributed to a fund at the University of the Free State’s (UFS) Centre for Accounting to give recognition to top achievers in the third-year programme for the B.Com. and B.Com Hons. degrees respectively this week. It is evidence of the good relationship that exists between the Centre and the South African Institute for Chartered Accountants (SAICA), Free State. Here, from the left, are: Mr Pieter Clase, CoetzeeSmit Chartered Accountants, Mr Oswald Wentworth, KPMG, Mr Ettienne van Niekerk, PricewaterhouseCoopers, Herman Leach, Gobodo Inc. Chartered Accountants, and Mr Stefan Strydom, Havenga, Rossouw & Viljoen; front: Mr Ian Smit, Enslins Bloemfontein, Ms Thelma Crossman, Mazars, and Ms Daphline O'Brien, Ernst & Young.
Photo: Stephen Collett

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20 April 2009
Faculty of Education, Faculty of the Humanities.

CHESD awards 15 masters degrees
A group of 15 students received the Structured M.A. (Higher Education Studies) of the Centre for Higher Education Studies and Development (CHESD) at this year’s autumn graduation ceremony of the University of the Free State (UFS). This is the biggest group in the centre's history to be awarded master’s degrees, while four of the students received distinctions. Also of interest is that six of the 15 students already have doctoral degrees. At the occasion were, from the left: Dr Dipane Hlalele, Qwaqwa Campus, Ms Liesl Hoare, Central Univeristy of Technology, Welkom Campus (best achiever), and Dr Fanus van Tonder, Programme Director: Higher Education Studies and Research, CHESD. Ms Hoare received the Deans medal in the Faculty of the Humanities as the best master’s graduate student at the graduation ceremony. At the faculty’s prize function she also received the Kovsie-Alumni Trust award as the best M.A student in the faculty. She also received the CHESD Prize for the best achievement in the Structured M.A. (Higher Education Studies).
Photo: Leonie Bolleurs

UFS awards degrees at autumn graduation ceremony
Five hundred and eighty six degrees and nine doctorates were awarded this week during this year's autumn graduation ceremony on the South Campus of the University of the Free State (UFS) to students in the Faculty of the Humanities. At the occasion were, from the left: Nicola Bekker, Madré van der Merwe and Esté Scholtz. All three the ladies received the qualification B.A. Language Practice.
Photo: Lacea Loader

This year’s autumn graduation ceremony of the University of the Free State (UFS) is held on the South Campus in Bloemfontein. Today a group of students from the Programme: Governance and Political Transformation in the Faculty of the Humanities received their qualification. From the left, front are: Dr Tania Coetzee, Head of the Programme: Governance and Political Transformation, and Mr Itumeleng Liba, Chief Operation Officer at CENTLEC; back: Mr Kennett Sinclair, Vice-Chairperson of COPE in the Northern Cape, Ms Nicole Joannou, Goldfields Business and Catering, and Mr Tembeni Lobe from Bloemfontein.
Photo: Lacea Loader

Some of the students who received their qualifications during this week's graduation ceremony of the Faculty of the Humanities were, from the left: Shu-Jung Chan, B.Mus. Hons., Brian Gxavu, B.Mus., and Mpolokeng Lepote, B.A. Media Studies.
Photo: Lacea Loader

UFS’s CHESD awards doctoral degree
Ms Mardi Delport (middle), Assistant Director: Media and Communications at the Central University of Technology received her Doctoral degree at this year’s autumn graduation ceremony of the University of the Free State (UFS). The title of her thesis is: “An internal communication model for the Central University of Technology, Free State as a multi-campus institution”. With her are her promoter Prof. Driekie Hay (left), Vice-Rector: Academic Planning, and her co-promoter, Prof. Annette Wilkinson (right) from the Centre for Higher Education Studies and Development (CHESD) at the UFS.
Photo: Leonie Bolleurs

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