A rooftop hops farm in the city

Hops are traditionally grown in the Western Cape, but on a rooftop in Johannesburg, Khaya Maloney has shown it is possible to grow hops in the city using a hydroponic system.

A rooftop hops farm in the city
Khaya Maloney
Photo: Peter Dempsey

Khaya Maloney grows hops using a hydroponics system under cover on 300m2 of space on a rooftop on Constitution Hill in Johannesburg. The space is leased to him. Using this set up, he can produce four harvests a year, instead of the single harvest that traditional hops growers achieve.

While Maloney doesn’t have a formal background or training in agriculture, he has a qualification in construction engineering, with experience working in fintech start-ups. He always knew he wanted to become a farmer, but not in the conventional way of using open land.

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He followed his passion for business and innovation and took the leap to become a farmer after he saw a project in New York that involved growing vegetables on rooftops. He says that Minerals Council South Africa had a similar initiative aimed at putting 100 greenhouses on rooftops, and he approached them with the idea of growing hops, instead of vegetables, using a hydroponics system.

“The initiative aims to create an urban agricultural ecosystem by repurposing disused rooftops to produce agricultural produce for Johannesburg’s inner-city communities,” he says.

He then joined the incubation Wouldn’t It be Cool project, run by the Urban Agriculture Initiative (UAI). This project receives support from Minerals Council South Africa, National Treasury and GWK, amongst others.

Hops are a versatile crop with essential oils that can be utilised in the pharmaceutical and cosmetics industries.

After completing the UAI’s eight-week programme, which offered training on business management and hydroponics systems, he received R250 000 in funding to establish his rooftop farm.

“Since I needed specific controlled-environment technology, [the UAI] agreed to co-fund my farm for R512 000 [instead of the R250 000 offered to other graduates], which I paid for using my previous agricultural grant award prize money.”

Using this funding, he set up his four-season hydroponic hops-growing facility.

“One of the reasons I chose hops is because I realised they use tons of water, a lot [of hops]aren’t sourced locally, and they degrade over time.”

This meant that there was a market for his product, particularly amongst craft brewers. Maloney uses the Dutch buckets system of hydroponics. He started small, with just 10 buckets to experiment with the crop, and realised hops are a crop that are very sensitive to temperature changes and the elements.

He says they are better managed in a temperature-controlled environment, using sensor-operated precision farming and a timed hydroponics system. The hops are grown in nutrient-rich water, which nourishes the roots directly, resulting in multiple harvests a year.

Producing quality hops
After growing 10 buckets of hops successfully, Maloney contacted various suppliers to help him build a greenhouse according to his specifications.

The greenhouse is 30m x 10m x 7,5m, and is temperature- and moisture-controlled. Maloney has already harvested twice in 2021, and while hops are mainly known as an ingredient in beer, Maloney says they are a versatile crop that produces essential oils, which can be utilised in the pharmaceutical and cosmetics industries.

Maloney adds that hops are a fickle crop that have to be properly stored within six hours after harvesting.

“Usually, hops are dried in a kiln and pelletised shortly after harvest to preserve and store the product.”

The ‘dry’ hops are then added late in the brewing process.

However, Maloney uses the wet-storing method, in which the hops are vacuum-sealed and kept fresh long after harvest, instead of being put in a kiln.

Maloney says finding suitable cultivars was a challenge, as the majority of hops grown in South Africa are protected by plant-breeder rights, so he currently uses three imported cultivars, namely Krakenup, Cascade and N-A-K.

Dutch bucket system
Maloney uses the Dutch bucket hydroponics system. He has one large reservoir tank that holds 5 000ℓ of water and nutrient fertiliser. A submersible pump is placed in this reservoir to pump the nutrients into the drip-irrigation line. He uses micro-drip irrigation. The drip emitters are placed in the buckets where the crop is grown. The whole system is automated, and runs for 20 minutes every four hours. The water is recycled in the system.

The buckets are 12mm x 50mm net pots, and Maloney uses coco peat as the growing medium. Each plant receives around 8ℓ of water/ day.

“Hops enjoy nitrogen-rich soil, and I’ve had to mimic the conditions in George where they are mainly grown,” he says.

The temperature-controlled system consists of air conditioners for winter, as well as carbon dioxide extractor fans and sensor-controlled pulsators that drop the temperature dramatically during hot summer days in Johannesburg. The system is controlled by sensors that monitor the temperature.

Maloney has 550 hop plants, and currently yields around 300g/plant. This means he harvests around 150kg/ season. The optimum yield is 700g/plant, but Maloney says he is still experimenting with the system. The ideal growing temperature for hops is between 30°C and 35°C, but these vary between cultivars.

Maloney aims to scale up his production with a single cultivar, Krakanup, as this is the preference of craft brewers. He has a mentor who assists him with his growing operation and cultivar selection.

Markets and clients
The market for hops is growing, and their versatility has allowed him to produce for more than just the brewing industry; he has received orders from the hospitality industry for essential oils, which is used for cooking purposes.

The essential oils that can be extracted from hops is also an extremely valuable commodity, he says. Maloney says there has also been interest from tea companies that use hops to create a hops tea. The home-brewing industry is also creating a steady demand for his product, which is currently exceeding his supply capabilities.

One challenge he faces, however, is that ‘dry’ hopping is the more common method of brewing, and he says that he is doing his best to educate brewers on using ‘wet’ hops.

Growing medium
As hops are not grown from seed, growers use plant rhizomes. Maloney grows the rhizomes in coco peat, which is an organic medium made of coconut husks and other nutrients.

The medium offers excellent water and oxygen retention, and provides for high-quality root structure and plant yields.

Maloney says the coco peat is similar to traditional soil, and allows nutrient-rich water to flow through the top of the bucket and out through holes at the bottom, into the irrigation pipes and back into the tank.

He tests the pH of the water in the filtration system on a daily basis, using several devices that provide an exact reading of the water’s nutrients, and is able to adjust the levels accordingly. He says the ideal pH is between 2,4 and 2,6.

Two water tanks feed the misting pulsate system, which can instantly cool down the greenhouse when the temperature gets too hot.

The plants receive additional light through the use of compact fluorescent lamps that are on a timer to trick the plants into thinking the days are longer.

Because the hydroponics system allows for a controlled environment, he does not have major problems with pests or diseases, but he implements preventative management of root rot, aphids and algae.

He adds that hop rhizome plants have a lifespan of around 25 years and can be propagated from the bine or cuttings.

“The input costs are high. The complete system costs around R500 000, but the return on investment per year can be up to R462 000 if you can get the yield up to 500g/plant,” he says.

Maloney says that, ideally, he would like to grow the operation and have a 1ha greenhouse at a single location.

“The potential to create urban farmers and offer employment opportunities is huge,” he adds.

Email Khaya Maloney at [email protected]