The Sustainability Prize


I recently had the chance to interview 2014 Prizewinner Antony Castro Rivera about his graduation project, “Implementation of Model Adaptations for a Sustainable Urban Home in Heredia, Costa Rica,” which turned his family home into a sustainable and profitable entity. I caught him right before a backpacking trip to Rio, where he plans to do some traveling before scaling up his hydroponic lettuce business!

This interview has been edited for content and clarity.

On the inspiration for the project:

At the time I was deciding on my project, I read about an animal called a pyrosome, informally called a sea unicorn in Spanish. It looks like a single organism, but it belongs to a classification of animal called a zooid: a collective of individuals that acts as one, similar to bee colonies. That was my specific inspiration. I was looking at these animals and thinking about my home as a home-sized fishbowl. I thought about we as humans as a kind of pyrosome, with external individuals protecting the internal ones, and the internals providing food to the external. I wanted to make my home a kind of example, and I wanted to become a seed disperser in my community: not just with vegetable seeds, but with microorganism seeds and earthworm seeds for sharing. I wanted my home and my community to start functioning like a zooid.

About the project itself:  

The idea was to make my home “blue flag” sustainable. Then I realized that the certification is meaningless and you can do everything better on your own, outside of the certification bureaucracy.

I started investigating. I found that there is a lack of information necessary to determine what human intervention means in this context, so I decided to provide a theoretical and practical framework of my experience as an economic and technical reference for others who would like to do the same thing.

I started looking at my surroundings and broke everything down to the basics: water, light, heat, food, the wastes we all produce. I took into account that time equals money for most people. That gave me the basis for building my model.

I quantified all the wastes my home produced during the study time and determined recycling methods for plastics, paper, cans, etc. I gave our recyclables to people in the community who work in this area, and who will pick it up for free. Like in the zooid model, it gives them revenue and they are happy to come get it, and it contributes to wastes not ending up in the garbage.

I started checking global methods for disposing of organic wastes. There were two very promising methods: earthworm composting (vermicompost) and a Japanese method of creating microorganisms for compost with fruit peels, salt, dairy cultures and sugar. I followed both of these methods and made earthworms from the seed, as well as microorganisms, for sharing with others.

For the energy factor, I borrowed a voltmeter from the university and measured all electro-domestics to determine the biggest power consumers as well as the time of consumption. I made this document available for others in the community to be able to determine their own domestic electricity consumption patterns.

I projected the viability of installing solar panels, but it wasn’t economically viable because we didn’t consume enough energy to qualify for a lower price. I started looking around for other possible adaptions, and found an example of a local guy who had made a solar water heater. I included his work in the study with instructions of how to do it. It’s viable and it works! The electric water heater accounts for the most consumption in our home, so it reduced our energy bill by 20%.

I also made the projection for rain collection on my roof based on local meteorological data, and determined that it was viable. Here it rains a lot! We made the adaptation and we got lots of water. Unfortunately, you can’t drink it or use it on the skin because it has some microorganisms. But it can be used for washing the car, cleaning, stuff like that.

The economic, social and ecological impacts of the project:

The project had to have a very convincing economic element for my family. I decided on hydroponic agriculture, and made about 100 pounds of hydroponic plants. I invested mostly in lettuce, because you can consume it all day in salads. We decided to sell it with its roots, so it’s still alive and people are getting contact with a live plant. Many of them saw it as so beautiful that they didn’t eat it, just left it to produce flowers in the kitchen. That was an interesting reaction that I didn’t expect.

I made the hydroponic concentrated nutrient solution myself and compared it with the one available on the market. We found that a solution is 10 or 20 times as expensive to buy than to produce, and micronutrients are 60 times more expensive on the market than to self-produce. The market doesn’t reflect the real cost of these solutions. So people can do it themselves! It’s not as expensive as they say.

In terms of profitability: In the beginning of the project, you have to invest in infrastructure, which will take time to cover with revenue. Within a matter of two years, however, you can be paid back for all of the costs associated with infrastructure and manpower. This year, 70% of my income came from the 1,000 lettuce heads, and 3% from chiles and small food items, including medicinal plants. I am currently making projections for 2,500 lettuce heads, which would make the project more viable.

Every month the project generated 8.5% of an average Costa Rican base salary, so over the course of the year it would generate 102%. That’s an extra salary per year, which for a low-income family would represent a big windfall.

It also adds ecological value to your field. We’ve seen more lizards, more spiders, more birds. We even see bees pollinizing different plants. There is ecological synergy, and if you share spaces with your neighbors then you have economic synergy, too.  If you have 12 people in this system, you would have the equivalent of an extra person producing revenues for everyone. Not to mention the social aspects—giving the children hobbies, which is important in my neighborhood, where children have very hard experiences.

One major element was the live, biological assets. They make the project more interesting from an economic standpoint because of their reproductive capabilities.  For example, you have 1,000 earthworms for composting, and you share them with others, and in a month you will recover everything you shared and the others will have the same. It’s been pretty neat with my closer neighbors. I tried to share specifically with people who already grew some medicinal plants, people with some agricultural area, families with children. I tried to involve all the children I could! But the people I was most interested in were university-age people, because of the fire we feel inside. We know that we need seven planet earths to survive and that we have just one. It’s ingrained in us and so we are working together to create synergies: You know about architecture? Ok, help me with this part. You shouldn’t do it with that percentage sand, you can do it better by combining these materials. Thank you very much, here take this seed. And we keep in contact and we share.


It’s not as romantic as it looks! I had some problems. The corn I planted outside was stolen. A girl was using it to feed her macaw. My sunflowers were also stolen. I told the kids who stole it: when you plant, you have the right to harvest, but if you don’t plant, you don’t have the right. After that, they helped me plant beans and they saw it wasn’t as easy as they thought. They saw the work that goes into it, and they also had the experience of planting their own crops. I saw it as a positive in the end.

How his family felt about transforming their home:

They feel good about it. They have been exposed to the process through the university and through my and my sister’s school. They’ve become aware of the situation at the global scale and they are concerned about doing something for us, for the planet, for the animals. They are happy to do it in our home.

We had been thinking of building apartments off the house and I told them not to spend money on that, and that I would provide something different, and even more beautiful and satisfying, and they said “Ok, Tony, we’ll give you a year. Show us it’s viable and we will see.” They were satisfied.

How others felt about the project’s viability:

I was invited to the public university in Costa Rica to present this project to the students. Then, I asked them to complete a survey. I found that the people lack information, but they are interested in these home modifications, and they think it’s viable as a means to creating independence. People are looking for ways to reconnect with the agricultural past of Costa Rica. I also surveyed my neighbors, who told me that they have the space, but that time is a limiting factor, which is why I tried to make these adaptations “cheaper” in terms of time. For example: because we had lots of water, more than we could use on the plants, my father and I developed an idea for a gravity drip irrigation system. I developed some prototypes of the drip parts on my own, since gravity dripping is viable but not yet available on the market. Gravity irrigation means people would just have to open the system and let the water flow and all the plants would be irrigated. They wouldn’t have to go one by one, which is a big time limitation.

Antony’s Short-term plans:

Having a white sheet of paper in front of you after four years of university is an interesting sensation. I really love backpacking, having only necessities, and sharing with people in different countries (not just hotel people). I love contemplating landscapes. I’m hoping to do that for the next two months.

When I get back, I’m planning to produce my own microenterprise to expand into 2,500 lettuce heads with roots. When I do that, I will have my income capital and if everything goes as planned, I will invest in a 3D printer to further develop the prototype for the gravity drip irrigation system. I’m interested in developing printable models for gravity drip irrigation to send by mail, the digital files you need to print them on your own 3D printer, as well as the tutorial you need for installing it.

I’ve also started consulting at the university, producing soldier fly production for their wastes, which can be converted into animal feed. Right now, the production is 20 kilos per day, but I know we can produce more with some adaptations.

Long term plans:

I started my education studying economics and finance, but I realized I don’t want to work in an office all the days of my life, so I went to EARTH to be in the field. It was a nice experience, but I don’t want to live in that world either. I think I’m more of a hybrid, which is why I’m interested in urban agriculture.

All my life, my favorite hobbies have been to contemplate stars and read about quantum physics. We are living in an era which will lead humanity to another scale and quantum helps comprehend these processes. In the future, I really want to study physics. That’s my goal.

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