Latest News Archive

Please select Category, Year, and then Month to display items
Previous Archive
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

UFS presents first Beyers Naudé Memorial lecture
2010-09-16

At the Beyers Naudé   Memorial lecture were, from the left: Prof. Jonathan Jansen, Rector and Vice-Chancellor of the UFS; Rev. Cedric Mayson; and Mr Kgotso Schoeman, Chief Executive Officer of Kagiso Trust.
Photo: Dries Myburg

The seventh Beyers Naudé Memorial lecture was presented for the first time at the University of the Free State (UFS) this week. This lecture that is presented at a different university each year took place on the Main Campus of the UFS in Bloemfontein this year. Rev. Cedrick Mayson presented the lecture with under the theme: Crafting a legacy.

According to Rev. Mayson more deeply rooted forms of suppression came forward after the democratic elections in 1994. Liberation from apartheid was, according to Mason, very superficial. The poor were still severely suppressed at economic, political, cultural, religious and environmental level. “We have to apply Beyers Naudé’s legacy of liberation in these areas,” Rev. Mayson declared.

“The system according to which the rich become wealthier and the poor become poorer must be replaced by a system where everybody can have enough. This is only possible with the insight of the oppressed.

“The government and the opposition are dominated by people who seek advantage for their own gain. Regardless of democratic slogans and some enlightened individuals’ rules against corruption and violence, we lack the political will to engage in the transformation of the whole world for the good of all earthlings,” said Rev. Mayson.

According to him, consumer culture has become a fine-tuned instrument for keeping people incomplete, shallow and dehumanised.

“Religions are self-centred. Leaders from most of the religious groupings criticised apartheid but they never joined the struggle to assist in demolishing apartheid. It appears as if religious institutions are not able to address the causes of poverty because they themselves are too rich and too powerful,” said Rev. Mayson.

He ended with the following words: “What we need is a leap of faith. Beyers knew that. The world is waiting for people to claim their legacy and to accomplish a post-religious secular spirituality of ubuntu.”

Rev. Mayson is a former Head of Religious Affairs of the ANC. He had also been a former staff member of the Christian Institute before it was banned. Furthermore, he was the Editor of Pro Veritate. Before he retired, he had also been involved in the South African Council of Churches and the World Conference for Peace.

The memorial lecture, a collaborative effort of the UFS and Kagiso Trust, endeavours to involve South Africans in dialogue about issues that affect our nation. This year the lecture was presented at the UFS for the first time and it will take place on the Qwaqwa Campus of the UFS next year.

Media Release
Issued by: Mangaliso Radebe
Assistant Director: Media Liaison
Tel: 051 401 2828
Cell: 078 460 3320
E-mail: radebemt@ufs.ac.za  
16 September 2010
 

We use cookies to make interactions with our websites and services easy and meaningful. To better understand how they are used, read more about the UFS cookie policy. By continuing to use this site you are giving us your consent to do this.

Accept