Urban Ecosystems - Closing the loop

Hemmaodlat is competing in an innovation competing where the goal is to use residual heat and to grow food sustainably in an urban area. This is a part of our proposal.

Av Niklas Hjelm

Overview

Our greenhouse is divided into four main sections, each playing a crucial role. In the heart of our greenhouse you will find a café that serves fresh dishes with produce from the greenhouse. Here, our educational tour starts and which lead you into our tropical section where you can pick your own fruits. In the café Koi fish swim in tanks to provide both a relaxing environment and the vital nutrients for the plants. The double height of the greenhouse provides a mezzanine floor that acts as an terrace, with more space for seating and better view of the greenhouse’s different sections.Behind the scenes, waste from the café and greenhouse is being shredded and put to use feeding the black soldier fly larvae, which in turn will feed the fish, closing the nutrient loop. Next to it, heat is powering a turbine, converting it into electricity which powers equipment used in the cooler production area. In here, rows of neatly stacked towers grow leafy greens vertically, saving much needed space and making harvesting easy. Vast quantities of lettuce and herbs are grown for use in the café but most are delivered to nearby stores and restaurants. LED lights provide much needed supplemental lighting for the darker months. This enables year round production within the city using organic growing methods.  The novelty in this idea is connecting the four pillars of sustainability: the social, environmental, economical and the cultural aspects together in an integrated way. Let’s begin the journey.

1. Collecting, saving and using energy in a smart way

Harvesting residual heat

Depending on the site location, access to residual heat varies depending on the type of industry present. Infrastructure in the form of pipes also differ, where the most common temperature sent out in the grid is between 80-100 degrees celsius. Lower temperatures are sometimes also available. Connecting Urban Ecosystem to the residual heat grid requires the collaboration with the local energy company invested in the area, such as Kraftringen or EON. Depending on the available heat source, we can either use a heat-exchanger to feed the right temperature to underfloor heating within the greenhouse, or we can first use it for the conversion to electricity using ORC.

Producing electricity from high-temperature sites 

Transforming heat into electricity has many advantages, it can be used to produce both heat, cold, mechanical work, and light, all of which are used in a modern greenhouse or fish farm. To produce electric energy from residual heat, a method called ORC (Organic Rankine Cycle) can be used. This is similar to a steam turbine generator, but instead of water it uses an organic fluid which enables the turbine to work on a much lower input heat from the incoming water.

Saving energy using the earth as an air heat exchanger

The greenhouse is also connected to an open cycle Earth Air Heat Exchanger (EAHE) for natural ventilation. EAHE is basically an underground heat exchanger that can absorb from and release heat to the ground. Earth temperature at a depth of 3-4 meters remain stable all year round. This constant temperature characteristic is due to high thermal inertia of the soil, the deeper the depth of the soil, the less fluctuation of the ground surface temperature. In our proposal, we will be using the buried pipes for the EAHE system as open loop. Typically, air is blown in the pipes using an electric fan placed in the inlet. The temperature difference between the surface of the ground and below the ground due to time lag of heat transfer can be used for heating in winter and cooling in summer for the greenhouse. EAHE will keep the greenhouse indoor temperature stable within minimum range of 8 degrees celsius in winter and 11 degrees during winter season. The heat produced by the greenhouse users, machines and the lighting features are also calculated for their contribution in indoor heat gains. That means that we need only the waste heat for increasing the greenhouse indoor temperature from 8 to 19 degrees celsius in the production unit for leafy greens or 25 degrees celsius in the tropical zone.  In this way, we have excess waste heat to be used in electricity production and for water heating.  

2. Efficient production using organic methods

Rooftop greenhouse

Producing food year round in Sweden is energy intensive. Growing inside a greenhouse where we can use sunlight will provide light and heat during a large part of the year. Using supplemental lighting is an enormous waste of energy if used year-round, but necessary to prolong the season for year-round production. LED lights will be used in the leafy greens section, while double-ended HPS lights will work better in the tropical section.  In order to make production viable, land should not be taken into use, instead we propose fitting new rooftops to be able to handle a greenhouse with fish tanks. Refitting older structures to handle specific larger loads is also a viable option.

Managing humidity in the greenhouse

Ventilation in a greenhouse requires vast amounts of energy, but with the use of a Ventilated Latent Heat Converter (VLHC) provided by Agam, we can save up to 60% energy compared to traditional ventilation. It works by converting water vapor into water and heat by blowing air through a water absorbing filter in a cooling tower. While doing this, the condensation from the vapor naturally warms up the water absorbing filter. The heat produced is released into the greenhouse as warm, dry air. By doing this it converts the heat stored in water vapor into heat that can warm up a greenhouse, making more heat available for conversion to electricity.  Using this technique we don’t have to ventilate the greenhouse by opening up vents. This has many advantages; heat loss is reduced, the environment is easier to control and pests have a harder time finding their way to the plants.  

Greenhouse automation

Greenhouse automation is key to make an efficient inside ecosystem. With extended sensor use throughout the building we can discover and utilize all heat sources and transfer that energy in the form of heated air to where it is needed.  With smart building control, HVAC systems (Heating, Ventilation and Air Conditioning) can work together with greenhouse climate control systems and EAHE. By using sensors, control systems and expertise from companies like Regin and other HVAC system designers we will create a functional system which utilizes all aspects of residual heat and gases.

Water collection and use

Water will be collected from the greenhouse rooftop using gutters. It will be used for irrigation, flushing the toilets inside the café and for cleaning the greenhouse walls and floor. The water will be filtered used bio cleaning systems in collaboration with Melica Miljökonsulter and Alnarp Clean water initiatives. We aim to use the same know-how but with adjustment to suit our project purpose to a cost efficient and low impact solution. Sensors for water sprinkles will be used for self and auto-cleaning of the greenhouse. This will enhance the visual contact with the outdoor space and the efficiency for heating and cooling.

3. Aquaponics production

Sustainable fish feed production 

Today, the most common ingredients in fish feed is fishmeal and vegetable proteins. Finding a protein rich fishmeal that can be produced onsite is of vital importance if aquaponics/aquaculture is to become truly sustainable. Black Soldier Fly are insect decomposers which, during their larval phase break down organic nutrients and grow in biomass, making them suitable as fish feed. By designing the fly system in a specific way, it is possible to feed them with waste from the café, greenhouse and filters.. The collected fly larvae should be subjected to a process of mechanical defatting (such as using the eco-friendly MEPSI method) and then added to a fish feeder extruder to shape them into pellet form. In this way, the larvae biomass is more easily digestible for the aquaponics fish, allowing its use as a complete feed substitute. The decomposing performed by the black soldier fly larvae also produces a nutrient rich leachate, which can be used as a nutrient supplement for foliar or water application.

Choice of fish

The most common aquaponically grown fish type is tilapia. The market demand for tilapia however we deem as low. Considering the different range of fish species available when shopping, it’s unlikely consumers would choose tilapia in large enough numbers to make producing them cost-effective. Even if we would grow different types of fish, aquaponics limits the range to certain types of freshwater fish due to temperature, salinity, space, and other farming limitations. Specifically in the case of tilapia, there is also the factor that it must be kept in clean tap water and starved one week prior to harvesting to improve its taste. This information would likely deter some from buying farmed fish, especially in view of there being a strong local fish industry. Overall we believe the benefits (in terms of revenue, sustainability, social, and cultural) of producing a sufficient amount of fish would not outweigh its costs, both in terms of the animal cost as well as the added investment and operational costs, especially in an urban environment where land is more expensive. Therefore, in our solution we’ve decided to focus on plant production. The fish still play a vital part in feeding the microbes that create nutrients for the plants, but they also have a social and educational role. Instead of harvesting the fish with all the requirements associated to ensure hygienic production we’ve chosen KOI, an ornamental fish. While enjoying your meal in the café, KOI fish swim in tanks and ponds around you. Providing the nutrients needed for plant production, but also helping visitors understand the role they play in the urban ecosystem. KOI is widely available in Sweden and a hardy fish that doesn’t need restocking very often.  

Vertical production of leafy greens

We’ve partnered up with Re:Farmers, a distributor of ZipGrow towers. These vertical towers are perfect for aquaponic production since their biofilters have a very large specific surface area , which is needed in the nitrification cycle. They have a proven track record and besides being used by Hemmaodlat, are also used by companies like Freight Farms. Their light weight is an added bonus for rooftop production as older buildings might not need as much retro-fitting. In a normal configuration we can fit 3 towers per square meter. Each tower can hold 8 heads of lettuce or 12-16 herbs depending on how the latter grows. We can use a combination of cut and come again crops like chard, kale, basil and mint together with full harvest crops like lettuce and pak choy. Per 1000 SQM we can produce 24 000 heads of lettuce from seeded plug to harvest in 4 weeks. For cut and come again crops we can harvest every other week.

Self picking of Tropical fruits

To increase diversity, Nakhlatec with over 30 years’ experience in propagation and production of tropical crops, will oversee development of a growing area in the insulated central portion of the heated greenhouse. Plants from an extensive range of tropical and subtropical regions of the world will now be feasible to produce using residual heat, different citrus species and varieties (like lemon, limes and kumquat), pomegranate, dwarf varieties of papaya and fig bananas, passionfruit and soft fruits like mangosteen, rambutan and litchi. To raise rapidly adult flowering and fruiting specimens of shrubs and trees, a retinue of judicious grafting and budding techniques will be applied. Close collaboration with overseas commercial farms and nearby botanic gardens will source appropriate healthy certified seed for rootstocks and vegetative materials used for bud wood and scion materials. The latter will be multiplied when needed throughout the year using the special roller containment attributes of the planetary rotogro system for urban plant raising. Should visitors wish to purchase containerised plants for growing on at home these will be on sale in the café.

The area will consist of raised beds fed by aquaponic liquid feed. Depending on tree stature, 300 – 350 flowering and fruiting trees will be exhibited at any one time (based on a space of 1500 SQM). The tropical area will be laid out with assistance from Nakhlatec tropical partner - Terra Garden of Malaysia. With a 2-metre spacing between trees, 400 exotic greens will be positioned per raised bed providing 4 000 understorey leafy greens to be displayed at any one time. In order for fruit setting to occur, bumble bees will be used to pollinate the flowers. Pest and disease control will be implemented by introducing certified pathogen-tested planting materials into the propagation cycles, and secondly by deployment of standard IPM using biological control agents that can be supplied by Binab, located in Sweden.

Raising of seedlings using Rotogro

Raising of seedlings and scion materials as well as grafting operations will be carried out in a dedicated propagation space in the lower service level. This area will house a 3-metre long planetary rotogro supplying plants with suitably adjusted aquaponic solutions derived from filtered leachates and fish tanks used in production of the conventional temperate green salads on the upper building level.

4. Getting the produce to market

For most products getting the product from the production site to the customer in the least amount of time is key. This is off course true for vegetables and fruits as well, but with the difference that once you harvest, it starts to deteriorate. High quality greens is a must to ensure a premium price, therefore the supply and demand chain needs to be as efficient as possible. As the cost of producing year-round in a city greenhouse is much higher, the cost of waste is much higher and needs to be low. To insure quality we have two different ways of getting the produce to the customer as fast as possible.

For true utilization of urban agriculture it is most vital to ensure that the supply chain is optimized and short as possible. This to minimize waste, capital binding in the logistic chain and the ecological footprint of the production. Because urban agriculture is being done in the proximity of the end consumer there is no need for long shipping and ripening during transportation, the products will be grown in optimal conditions promoting a more fresh and nutrient rich end product compared to its conventionally grown and imported counterparts.

1. Self service in the tropical growing area
   By having the customer pick their own tropical fruits and plants, we allow for a new and unique experience for the end consumer. Not only offering tropical produce in urban areas the service makes the customer a part of the value chain and life cycle of the produce. The service provides locally grown produce that are picked at their ripest moment which gives them a unique flavour and unmatched freshness. The self-service model minimizes the need for labour by putting the process of harvesting in the hands of the customer, giving them the choice of produce maturity and esthetics. Ripe produce can be turned into new exciting dishes sold at the café.
   
   

2. Local demand-based production.
   If Urban Ecosystems is located on top or adjacent to a supermarket it could be integrated to that stores internal ordering system thus allowing for a demand driven production of locally grown produce in urban areas. This to minimize overproduction, waste and the need for transportation. The system would let the store manager to order directly based on historical data and be given the possibility to change coming crop cycles to better match customer demand. Since the production is located in the stores proximity there is no need for any packaging, making the produce even more sustainable compared to similar products on the market.
   
   Urban Ecosystems planned production, locally grown produce and short delivery distances create an opportunity of providing locally grown produce to other nearby stores, restaurants and cafés. The same system used by the supermarket will be used for other clients and customers. Through an online ordering system, the customer will sign up for a minimum period of buying a certain amount of produce during this period. The contract-based deal is to minimize waste and creating longer lasting sustainable customer relationships.
   
   

   The customer will be given 3 options regarding the pickup/delivery of the produce.

   1. By offering a discount the customer/clients handle the pickup from the Urban Ecosystem.
   2. The customer is given the option of a third-party delivery company handling the logistics.
   3. The delivery is taken care of by the staff of Urban Ecosystems utilizing public transportation or carbon neutral transportation alternatives such as electric bikes.

   5. Education and culture

   Learning should be fun and relaxing. While enjoying your in-house produced meal, small screens provide information on how the food got to your table. If that’s not enough you can take one of the tours and pick your own fruits while doing so. If you need more inspiration, stop by the café again and learn how to best prepare the fruits and vegetables you just bought. While there, you can sign up on a special cooking class hosted by local chefs. For students there are several options to learn more; for instance, through internship programs and study visits. But it’s not just about the food and environment. Culture also plays an important role. On certain dates we celebrate diversity through art exhibits, music performances, and other social events. The greenhouse is more than just a place where food is produced and eaten, it’s an open and welcoming space for everyone to enjoy and learn from.

   6. Sustainability

   With climate change happening right now we need to be able to produce food without the need of external inputs. By growing in a resilient urban area, locals will gain a better understanding of how food is being produced and what is required to do so. This understanding can lead to less waste as an increased respect for the produce is gained. Having locally grown food also means less transportation of fruits and vegetables, lowering the exhausts and noise in the nearby community. We want:

   Engage more people: A large scale aquaponic greenhouse will be the subject of many discussions and will therefore lift the topic of sustainable agriculture and locally grown food. It will also be a great chance to engage more urban citizens in issues related to their future food security.   

   Sustainable consumption: Increasing locally produced food will help the issue of sustainable consumption by letting the consumer be closer to the production and therefore learn more about the process. This will strengthen the bond between producer and consumer to gain a better understanding of each other. Letting the consumer be a part of the process, by giving them the opportunity to pick some of their own vegetables, will also bring the consumer closer to the production process. That will raise the value of the food and lead to less food waste.

   Reduced chemical load: Utilizing fish waste as a nutrient source will reduce the use of mined minerals and synthetic fertilizers. The closed nutrient cycle will have a positive effect on the chemical load in nature and overfertilization from agriculture.

   Climatization: Producing food in a greenhouse makes it easier to protect crops from extreme weather conditions. This way of growing can be one way of preparing food security for future climate change.