BUILDING GOODNESS

with Michael Repkin In 2015, Omni Ecosystems ecological designer Michael Repkin helped the Studio establish our rooftop prairie. We spoke with Michael about the advantages of green roofs, the benefits of microbes, and the value of green spaces in urban areas.

What was your introduction to green roofs?

In the 1980s I worked on desert revegetation research and the microbiology of colonizing Mars, and I found that my interest in growing vegetation in hyperhostile environments was applicable to rooftops. Roofs are a horrible place to try to grow things—they can be subject to 165 degrees Fahrenheit, 100 percent sunlight, and one hell of a wind load.

So as an offshoot of my other research, I began to develop what is now Omni Ecosystems’ ultra-lightweight green roofing system. Most green roofing systems were codified in Germany to manage stormwater; they weren’t necessarily intended to grow vegetation or to create ecosystems, although some did so by default. And most of the green roof industry continues to look to that German model: essentially a stormwater system that might grow some vegetation. My work was to push that model further, to allow green roofs to produce food, fuel, and fiber for humans; engage other organisms to use it for habitat, food, and raising their young; and to cool the planet along the way.

Earth needs vegetation. We are in the midst of planet-wide de-vegetation and extermination of ecosystems. Buildings have been vilified for taking away from natural systems, and they have, but we also need them as habitat for humans. So if a meadow is destroyed and replaced with a building, the question is, can we put the meadow on top of the building? It’s not necessarily going to be 100 percent of that meadow, but it can still provide humans with food, provide animals with food, create vegetative cover, and filter water. It will create clouds through evapotranspiration. It will cool an area. All plants act as little umbrellas, so they’re not only mitigating carbon dioxide, they’re also shading the earth. If we have these little umbrellas everywhere, we prevent solar energy from striking an unprotected surface, like a blank rooftop, that absorbs the heat and re-radiates it at night.

How do you establish a green roof?

Step one is ensuring that the roof membrane is intact and has the needed structural capacity. This is first and foremost—ensure that the building is protected. Once this is the case, you can then add more armor. My team at Omni Ecosystems adds multiple layers of armor to ensure that our system does not interfere with the building in any way. Then we install our growing media, get it hydrated, and add biological nutrients.

How deep does the growing media need to be? What is the optimum depth?

It really depends on what the plant is and what your objectives are for it. For us, the absolute minimum depth of growing media required is below half an inch. We’ve been able to get plants to flower in a depth that shallow. On the high end, we’ve gone up to 36 inches deep.

For optimum growth, we start with a minimum depth of 3 inches and sometimes add a foot or two more, depending on the species involved. Your green roof at Studio Gang includes trees, so your depth ranges from roughly 5 inches in most areas to 18 to 24 inches where you’re accommodating the root balls of mature trees. If you’d planted those same species as small saplings, a few of them could be growing in 5 inches of media. They would take a while to really

develop but they could anchor in by putting out lateral roots for support.

What do lateral roots look like?

Depending on the species, it is very intimate root entanglement. It actually provides an incredible amount of support and resistance for trees and other vegetation planted in very shallow media that can experience high winds. With cross-stabilization and interlocking roots, green roof plants are more resilient to wind stresses than plants on the ground. They become a somewhat unified mass.

Will the greater intimacy of the root mass affect disease transfer?

We put a lot of disease resistance in the media. Let’s say that somehow material has been sprayed onto the roof that contains certain pathogens. They’d be outcompeted fairly fast by the microbial community within the media. In a relatively sterile situation, on the other hand, pathogens can take root. A lot of nurseries have turned to sterilized soil and media, and it’s a good thing because it’s less likely to spread disease or weeds, but it also means that the moment a root-born pathogen is introduced, there’s nothing present to outcompete it. It’s just like with the human body, which is normally loaded with beneficial microbes that cohabitate with you. When you remove those microbes with heavy antibiotic therapies, you basically have no defense other than your white blood cells against invaders.

So one of the abilities of the growing media is this inherent competition for microbial invaders?

Right. We developed the Omni InfinityTM growing media with that in mind. It was primarily developed for meadow-type situations but also for food production— thinking about food pathogens and how we prevent disease transmission. We were able to look at a lot of the problems that had occurred with other systems and other horticultural thought and ask, why don’t we fix that, why don’t we change that around? Let’s make the media lighter, for example, and in lieu of sterilization, why don’t we create a very dense microbial ecosystem? We want to do things better, which can mean challenging common horticultural practices.

What’s the water capacity of the media?

It depends on total depth and media, but generally it’s about 52 percent of the depth—so if you have 5 inches of media, it can hold about 2.5 cubic inches of water. It’s important to point out, though, that this is the saturation point, and the holding point can be greater. A lot of our media has a very high surface area; therefore, it’s adhesion of water to particulates rather than absorption that provides a very high water holding capacity.

The surfaces of the particles are so textured that one cubic foot of our media has roughly the surface area of a football field. It does not behave like a sponge because it does not allow water to penetrate in, rather it allows water to adhere. Once you reach a point where all of those little troughs and cracks and peaks are filled, additional water can also be held between the particles.

Water capacity also depends on the drainage system and the design objectives. We could actually have a system that would behave like a marsh. Or we could have one that was very, very dry. If you wanted to grow prickly pear cactus, let’s say, you’d want that to be a pretty dry system—you’d have a water cycle maybe once or twice a week. If you wanted to grow cattails, you could do that by changing the drainage pattern and changing the outlet capacity to flow outward.

So irrigation and drainage are key. And the actual material, what is that?

Let’s just call it geologic material . . . it gets put down with other materials that we’ve developed that are proprietary too.

One thing that is more important—since the 1980s I’ve been developing a library of microbes. All of those microbes— hundreds of species—end up going onto the roof. They take inorganic chemicals and, through metabolizing them, produce organic matter that can fuel growth. There are also biologically beneficial minerals being generated on your roof media through similar processes.

There are some really miraculous processes that we’re only just learning about, and it’s exciting to think how they can be applied to green roof systems. There’s already some anaerobic marshes that have been developed on green roofs, and there’s a lot of work being done right now on microbial fuel cells that’s aimed at harnessing that energy-producing activity of microbial life. Some of the microbes are being fed by plants. So there are all sorts of related processes that we can look at as we advance green roof systems.

Can you talk about the initiation process and what plants we selected, and how those plantings change year to year?

After the media is down, we have the infrastructure for growing all sorts of plants. But an ecosystem isn’t a static thing that comes fully formed; to make one, you have to think in terms of succession. You have to create conditions that are right for the next group of plants, which will lead to the next stage of ecosystem development, and so on. So generally, what we look to plant immediately are primary colonizers, species that establish stable growing conditions in the media by providing some raw biological material and fixing carbon dioxide from the atmosphere.

Early on we also tend to plant a lot of leguminous-type crops. These crops’ roots have rhizobia that can take in atmospheric nitrogen and generate nitrogenous compounds, which then turns into plant biomass containing proteins. When that plant dies at the end of the season, or when you cut it, it releases that nitrogenous compound into the ground. This is key because nitrogen is one of the chemical building blocks of life.

It’s a fertilizer, essentially.

Yes. In the normal world we have a constant array of organisms that are fixing nitrogen. We also have non-plant-based symbiotic organisms. To create similar conditions on a green roof, we include organisms in the growing media itself that take atmospheric nitrogen and turn it into nitrogenous compounds that can grow plants too.

With these primary colonizers and nitrogen-producing crops in place, we also plant species that are wanted in the future; they take more than one season to grow up.

Biennial Beeblossom

We’re just starting to see some of the biennials flower for the first time.

Once they get going, they’re good to go. What we would call a natural ecosystem in the wild would take many, many years of

development. But we can take fifty to one hundred years of time and squeeze it into a few seasons, so it’s a very biologically active, chaotic situation.

Once the primary colonizers start to take hold, some of the other plants really start growing. They’re going to make seed and propagate. From there your main job is to make sure that some new plants are added, or to take some of the seed from the crop you’re growing and spread it around to propagate it. Depending on how the wind is blowing and what temperature it is, more and more plants will develop.

You work with After School Matters, a nonprofit that runs after-school and summer programs for teens from Chicago public high schools. Some of these students helped harvest the wheat grown on our rooftop in 2016. What is your philosophy on how green roofs and urban agriculture can bring a community together and what that fosters?

Yes, Omni’s youth interns from After School Matters and One Summer Chicago worked on the Studio’s wheat harvest and threshing. It was a first-of-its-kind project for rooftops and for the students. The community that I generally work with is in the East Garfield Park and Austin neighborhoods. Over the years I’ve learned a lot from them about how they think about green space in an urban area. They tend to feel afraid of large open spaces; it’s not a place where they want to be.

Is it a personal safety issue?

Yes, absolutely. Safety is a real concern. One of my teens was just shot in the thigh walking down the street. He was just walking. But when you’re up on a roof, you’re no longer in that car zone; someone isn’t going to stick a weapon out a window. They can’t see you if you’re up on a roof.

When the teens come to Omni we do different things in different seasons. It’s not all farming or gardening. Sometimes it’s simply, let’s go to the roof. Sometimes we do stretching and yoga exercises. Here’s this place with all of these flowers and beauty and they don’t have to feel scared; it’s just vegetation. It’s that kind of immersion in the biological environment, that green infrastructure piece, that we’re trying to promote at Omni. How can we create these spaces in an urban environment where people can have meaningful experiences with nature?

To speak about the wheat harvest specifically, very few adults have ever seen wheat, let alone plucked wheat heads or winnowed or threshed it. Yet it’s the basis of civilization and a product we all consume today, a key storable grain. In addition to harvesting the wheat, the students got to work with bakers who mill their own flour to experiment with crushing and grinding it. To be very intimately involved with wheat, from harvesting all the way down to grinding— you learn what all these processes mean and come to value agricultural products more. It’s an incredible amount of work and just gaining that understanding, even if we stopped right there, would be a great accomplishment.

We were talking with ecologist Steve Apfelbaum about bioblitzes and the end of the conversation circled back to a similar idea. He was talking about how citizen science presents this same kind of opportunity to learn observance and cultivate appreciation. Even though that seems basic, it’s so vital and profound.

Absolutely. When you get to look closely at a square foot of wild space, suddenly it’s wow—an overwhelming amount of variation. One thing I told some younger students out in Evanston: “You guys can get your PhD out in the recess lot. Just take a spoon, dig in, and you will probably find a microbe that nobody knows exists.” That’s how rich our world really is, and we don’t actually know that much about it. Every time we really look, we find some amazing things. By bringing the green living world

to an urban area, where you can have an intimate experience with it—go up on a deck and be surrounded by all of these different species—you can practice that observation. Every time you visit, there’s growth, there’s change. Just to get that type of exposure is really important.

Also, you protect what you know. You protect what you love. If you don’t know something, it has no value to you. If you don’t know plants’ value or have never been around them, it’s easy to say, “yeah pave it over, whatever.”

I think that is one role urban agriculture can play. Up on your roof for example—a lot of the wild local plants are actually edible. Helping people understand that these plants are making sugar and vitamins, that they can sustain you, is very important. I talk about plants in terms of food, fuel, and fiber, not necessarily their value as living organisms but rather their relationship to you as a human being, why you need them. When someone is sitting in a lecture hall, learning about photosynthesis can seem boring or irrelevant, but we understand eating, we understand food.

Once a young student and I were talking about plants and photosynthesis. We created a fire and were boiling some water, and she had this kind of profound truth come over her face and said, “Oh that’s the sun’s energy coming out, that’s what the fire is” and I thought, “Yeah!” Here’s this girl in third grade and she totally got it.

We’ve lost a lot of intimacy with the living world. Bringing green space to people who are devoid of it is absolutely essential. There are all sorts of health and healing benefits associated with green spaces, and if we are constantly stressed and degraded and don’t have time to connect with nature—even if it’s a 100-square-foot plot of meadow—we’re just becoming sicker and sicker as a species.

With the current merging of architecture and ecology, we seem to be ready to change. We have a lot of people who are very ill and facing stressful circumstances, and green spaces can do so much for that. There are other benefits we’re just beginning to understand.

Studies have been done, for example, that measured the academic performance of kids facing green grass compared to kids facing parking lots. The students facing green performed better. Even though it’s not a jungle, it’s not a prairie, it’s just living space versus a place devoid of life, it seems to have helped them.

So I think it’s crucial to our future to have the benefits of ecological systems—

Winter Wheat

it’s psychological wellness, air filtration, storm water management . . . it’s so many different things. There is so much opportunity to make this happen—every building could have a green roof. Every building could contribute to this goodness and bring life back to cities. Places where they’ve ripped out that meadow, let’s put that meadow back. It’s very, very important work and I’m very glad to be part of it.

Michael Repkin is Director of Research and Development at Omni Ecosystems in Chicago. He is the inventor of Omni’s unique lightweight growing media and its food production system.

Passive acoustic monitors pick up ultrasonic bat calls that are then used to identify which species are in a specific location.