Today more than half the world’s people – 3.2 billion of them – live in cities, and all predictions are that this number will only grow. To feed a city, food has a long journey, both in terms of transport and the producer-consumer chain. That is why people are starting to grow their food where they live – in the city. Urban farming opens up new opportunities and finds new uses for spaces that are unvalued or, maybe, simply hidden from human eyes. Farms on building rooftops are a popular option today. One of the leaders in this field is the United States. 

We spoke with the creators of one American rooftop farm. Mary and Joseph Ostafi, founders of FOOD ROOF FARM (Saint Louis, Missouri), spoke with us about how a rooftop farm can turn places forgotten by the city into productive spaces, and how they were able to inspire city dwellers to grow food everywhere they can. 

– Mary and Joe, could you tell us about how your rooftop farm began?

Joe: We started doing urban farming in 2011 – we created community gardens in St. Louis. We had to keep jumping from property to property. The problem is that the land is usually owned by a developer or building owner, and they don’t want to let it go, so agreeing on rent is complicated – it’s hard to maintain something long term. We finally started to look up a different solution. One of our community gardener’s husbands owned a building in the city center. We asked if he had any interest in putting a community garden on top of this building. He found it to be an intriguing question, and we took a tour of the building. It was perfect because it was structurally sound and able to withstand the weight of putting a garden – or a farm in this case – on top of the building. Mary and I both have an architecture background so it was easy for us to visualize the possibilities. The owner of the building was looking for more revenue from his property, and everything on his property is rent-based. Our idea was attractive for him – it is normally an unoccupied space that brings in no income.

Mary: There wasn’t much opportunity on the ground because we’re in a dense urban environment.  Rooftops are the new opportunity.  

– How widespread was rooftop gardening when you began your project?

М: I wouldn’t say that it was widespread in our country. There are some rooftop farms in the United States, and we have been fortunate to learn from a few other rooftop farmers in Chicago, New York, and Toronto. But there were none in St. Louis, so ours was the first. 

– Is there any regulation of rooftop gardening? Does a building owner have the right to build a farm on his roof?

M: The project is zoned as a commercial property, so we’re allowed to put a business on the rooftop. Some cities, like Chicago, have specific urban agriculture ordinances that incentivize urban agriculture.  St. Louis is not quite there yet, so we just had to follow typical building codes.

J: We had to make sure the building could structurally support a farm. It’s a lot, as you could imagine – putting all that soil on the roof. It’s heavier than most roofs are designed for. The weight of the farm is five times higher than the weight of snow. We hired structural engineers to do an analysis to be sure the roof could hold it. That was probably the biggest regulation hurdle we had to get over.

– Construction must have required a lot of financial investment. Was it hard to get the necessary funding?

J: Our community has a long-standing track record for supporting agriculture, technology, innovative ideas, and philanthropy. All those things combined in our project. We’re a non-profit, so we rely on money coming in as donations. It took us a good part of two and a half years to raise the money, but we did do it, and were amazed at how supportive the community was.

M: Our largest funder was the Metropolitan Sewer District. We received a stormwater management grant.

Cities like St. Louis have very antiquated sewer systems, so there are a lot of overflow issues when we have storms. The Metropolitan Sewer District is trying to mitigate that, and we brought a unique solution – rooftop farms. Essentially a green roof system captures and reduces the amount of water that goes into the sewer system. As part of that grant we designed the rooftop farm to hold as much water as possible, and that’s not typically what a green roof system is designed for, but our farm can hold up to 17,000 gallons of water per storm event. So it was a win-win for us and for the Metropolitan Sewer District.

– Could you tell us more about the rainwater harvesting system, and the water supply system in general?

J: Most roofs have a water supply system, because you need it for the mechanical systems of the building. Things such as a cooling tower or a chiller are usually on the roof, so frequently there’s already a water supply through a standard spigot. So getting water to the roof isn’t the issue for us, but getting the distribution of water throughout the roof system was the challenge. We constructed an irrigation system to distribute water to the plants when they need it through a drip system.

Something to take into account is that over the winter everything freezes, so we have to drain all the water systems.

M: There are two ways we harvest rainwater. Our agricultural green roof has a retention board that is right below the soil – it captures water during a rainstorm. The water remains there until our plants wick it up through capillary action. During the next rainstorm, it gets replenished. The other way that we capture rainwater is the roof of the greenhouse. We have gutters on the roof and it gets routed into the greenhouse into a modular system where the rainwater sits until we use it to water the greenhouse.

J: Actually it’s a very standard European system. And I think one of the interesting things for us was that even our green roof specialist had to get a lot of materials from Europe. The green roof system industry in the US is a little bit behind Europe’s.

– What was the hardest part of the project?

J: Construction itself was a big challenge for us. The hardest part is that there’s not an infrastructure of builders that know how to build a rooftop farm. There are companies that have installed green roofs, and there are lots of roof contractors. A green roof for farming is something different, and there are only a few companies that have ever done it. It’s hard to find a contractor that does both as one package. So we had to stitch together a lot of disparate contractors ourselves.

М: Our profession really helped us in building the farm: as architects we were central figures and managed the building process, because we know how it had to look in the end. But it was very complicated, everything was very fast-paced, and we both had full-time jobs as we were doing it.

It was a new project type for us and the contractors. We learned a lot on our own, and it will come in handy in the future. Now we know how to do it faster, easier, and cheaper. 

J: We hired structural engineers, hydrologists regarding the rainwater capture piece, irrigation specialists, plumbing, a greenhouse contract, a green roof specialist, a soil agronomist, and a roofing system specialist. That was to get through all the city permitting issues, so it was a small but complex project that involved a lot of specialists.

Some people contact with us after finding out about us in the media. For example, the green roof contractor and the green roof specialist helped us get a grant.

And then yes, through my work there were a lot of building materials suppliers that we were able to tap into. Some of them even donated materials.

– What were the major costs?

J: I would say the new roofing system was probably the most expensive thing. Then the green roof came with the drainage boards, the soil, and the aggregate, etc.  Probably three-quarters of our cost was into those two elements. After that, the greenhouse was the next most expensive thing.

– How did you select which cultures to grow?

M: Since this was our first year, I wanted to experiment with growing as much as possible, so that I could learn and see what works best on a rooftop in our region. We knew that what grows best on a roof in New York or Chicago is not necessarily going to be the best for our microclimate. We grew sixty-two varieties of plants on the roof this year: ten different types of tomatoes, six different types of peppers, eggplants, cucumbers, herbs. We have seen what works best and now we are making a plan for next year.

J: Also we do research on a variety of different growing methodologies – like hydroponics, for example.

– Is your produce eco-friendly?

J: We advertise our products as being organic because we don’t use any pesticides or herbicides. We also like to use more heirloom-variety seeds and not hybrid seeds.

– How do the environmental factors in the city affect the farm? How does the farm handle the air pollution, the car exhaust, the dust?

M: Plants are actually extremely resilient and they’re excellent at filtering air. There have been studies that have shown that plants, especially food crops, grown in the urban environment are not that affected by air pollution. They’re more affected by soil pollution. So if you grow plants in contaminated soil that are high in heavy metals, they will soak it up through their root structure and it will integrate in the plant. So we need to watch the quality of the soil, which we do.

J: I want to note that sustainability is the basis of our project. When we conceptualized the project, we tried to make it as ecological as possible. We tried to create a closed-loop and a biologically-diverse space. Besides growing food we also created a pollinator garden for butterflies and other pollinators like bees, and put in beehives. Soon we will have chickens.

By putting a farm on the roof we are also reducing the temperature of the microclimate – we’re reducing the heat island effect, as we call it here in the United States.

– You spoke about how it is important to have healthy soil. How do you manage the soil?

М: The first year of the soil is always the biggest challenge because you have to build up the microbiology and provide nutrients. Due to weight restrictions we can’t add organic matter like compost, like we normally would. Plants get their nutrition through liquid organic products added to the soil. Different plants take up different nutrients from the soil. So we have to plan ahead where to put our plants to provide them with all necessary nutrition. Crop rotation is very important.

J: To keep track of the soil’s health and quality, we run tests. We take soil samples and give them to a laboratory at a local university where scientists analyze them. They give us a report of the pH and nutrient levels. That helps us to see what the health of our soil is, and what we need to do to balance it out or make it healthier.

– Who consumes the produce grown on your farm?

М: This year we donated 60% of our food. Since we started four years ago we’ve been partnering with St. Patrick Center, a charity that focuses on reducing homelessness.  The center has a café that is a training kitchen for homeless people to learn skills and then get a job in the restaurant industry.

We also have a community garden on the farm where people lease their own plots and grow their own food. I think that’s about thirteen percent of the food grown on the roof.

The rest of it we sell to local restaurants. This year I delivered food to several restaurants by bicycle. That way we have earned some income to offset all of the food we donate in the community. 

– I would imagine that you’re helped out by volunteers.

М: Yeah, I’m the only full-time staff. I run the organization and the farm. I have a group of volunteers that help on a regular basis and other volunteers that come on community volunteer days. We had at least a hundred volunteers on the farm this year. Some of them are students. Some of them are people who live in the neighborhood. Some of them are retirees, some of them are master gardeners… We have all kinds of people come and help out on the farm. Some people have never grown food in their lives and are really curious about learning. Other people have a lot of experience growing food and want to lend their expertise. We invite anybody to help out that’s willing to lend us a hand.

– Does the produce you sell compete on price with produce grown far away, shipped in, and sold in supermarkets?

М: Our produce is more expensive. But restaurants buy from us, because they know exactly where it was grown and by whom. It’s harvested and within ten minutes delivered to their kitchen. Besides, it’s a good story for their business to be supporting a local urban farm.

Food that’s grown locally and organically, whether on the roof or on the ground, is more nutritious because it’s getting to the restaurant or the end consumer a lot faster than conventional produce.

J: Financially we cannot compete with large food distributors for restaurants. Our farm is very small scale, and we cannot produce food at the same price as large distributors.

– Why do you do all of this?

J: We are a not-for-profit, non-commercial organization, as you have probably already realized. In the United States there’s a term – “social enterprise”, which I think aligns with what we’re doing.

М: A social enterprise is a business whose main focus is having an impact. So for us it’s an impact on society. Our mission is to grow healthy food while growing a healthy community. For us that mean putting a farm right in the middle of the city where people live so that people can come and experience the farm and learn from it and get inspired by it. First and foremost we want to engage people in the local food system, but we need a way to support the farm and pay the bills. To do that we sell part of our produce to restaurants.

We would love for people to grow food wherever they can, whether somebody has a backyard and they’re growing a garden, or they participate in a community garden, or they find a rooftop and start an urban farm. We hope that we can help them with that. The more food that we can grow in our cities that is being directly distributed to people in the community, the fresher it’s going to be, and the more resilient our food systems will be.

In addition to our charity work, we started partnering with local schools. A lot of schools have their own gardens, but wanted to see what it looks like on a rooftop. Some simply come on field trips, and for one nearby school we became a good outdoor classroom. We allocated a small portion of the farm for a youth education area. So the kids – they were second-graders – planted some food and watched it grow and harvested it. 

– In your opinion, how will food be produced in the future – in, say, 10, 20, or 30 years from now?

J: I think the future of urban agriculture is more rooftop farms, more vertical gardening, indoor hydroponic gardens. Of course, it still has its challenges in terms of profitability and commercialization – the scale needs to be significant.

M: Urban farming is going to gain momentum and is the way of the future. People are becoming aware of the food that they eat and demanding healthier, organic food. People support the local food system because they can get a glimpse into where their food was grown and they trust it.

– Are there projections of what percentage of the world’s essential crops will be grown by cities?

М: The Food and Agriculture Organization of the United Nations has recently reported that 800 million people worldwide grow fruits or vegetables in cities. They say that urban farms are currently producing one fifth of the world food supply. Since this trend is becoming more popular and more feasible, I would say that number is going to double within ten years, maybe even more.

– What advice do you have for people who are only beginning to build their rooftop farms?

М: For people who are just starting out, my biggest word of advice is to start small. That’s something that I’ve learned from other urban farmers. Start small with a big vision but gradually make your way up there.

The other thing is to leverage people like myself and Joe and others. We’ve gained expertise, we’ve built our farm, and now we’re consulting other people.

– What are your plans for the future?

М: This is our pilot project, and we’re learning from it. We hope to scale up to many other rooftop farms in St. Louis and actually beyond the city. We’re currently talking to a couple of building owners downtown who have approached us and are interested in building a farm on their roof. Next year we hope to have at least one more rooftop farm, maybe more.

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