The Vertical Ecosystem

What if a skyscraper could do more than provide a place for people to live or work? What if it could produce food, generate much of its own energy, recycle its water, recover nutrients from its waste, and turn materials that would normally be considered pollution into useful resources?

That is the idea behind the vertical ecosystem: a skyscraper designed from the beginning as an interconnected agricultural system rather than simply a building with a farm inside it. Crops would grow throughout much of the tower, while carefully designed areas could support livestock, aquaculture, food processing, water treatment, energy generation, and waste recovery. The goal would not be to make the building completely independent from the outside world. It would be to make the building exceptionally efficient at turning resources into food and energy while keeping waste to a minimum.

Crops

The concept starts with vertical space — something cities are surrounded by and rarely use for this. Stacking growing environments on top of one another lets high-value crops that do well in controlled conditions grow across many floors. Some areas could use natural sunlight, others efficient artificial lighting. The exterior surfaces could carry solar panels, so parts of the structure generate electricity while the interior produces food.

Livestock

Livestock would be a smaller but important part of the system. Cattle, pigs, sheep, goats, and poultry could be raised in specialised areas designed for their needs — but this requires considerably more engineering than putting animals on a floor of a skyscraper. Large animals are heavy, need substantial feed and water, generate significant waste, and require carefully controlled ventilation. The livestock component would therefore be much smaller than the crop component. The purpose is to integrate animals into the larger system, not to recreate a conventional ranch inside a building.

The methane problem

Animals introduce one of the more unusual energy opportunities in the building, and also one of its hardest problems.

Cattle produce methane through enteric fermentation, and that methane is normally released straight into the atmosphere. In a controlled building the air leaving livestock areas could at least be monitored and treated. But livestock methane is mixed into an enormous volume of ventilation air, which makes recovering it far harder than collecting concentrated biogas. This remains unsolved (see Open Problems below).

Manure is the easier opportunity. Rather than letting it decompose and release methane uncontrolled, it could be collected and sent to anaerobic digesters, which break the organic material down into biogas.

From biogas to power

Raw biogas cannot simply be burned. It is roughly two-thirds methane and one-third carbon dioxide, and in that state it causes aerodynamic problems in gas turbine components — even though its cycle efficiency is favourable. It has to be upgraded first.

Membrane separation can do this. In one recent study, a methane-selective membrane raised raw biogas from 69% methane to 97.74% purity at 88.53% recovery, operating at just 2 bar — low enough to be plausible inside a building, unlike cellulose acetate membranes that need 40 bar or more. Upgraded to that grade, the fuel performed almost identically to the natural gas the turbine was designed for. [1]

The detail worth pausing on: that membrane was made from biochar of spent coffee grounds, activated with potassium carbonate. A waste product becomes the device that turns waste into fuel. That is the entire principle of this building, demonstrated in a single component.

Once upgraded, the biomethane feeds combined heat and power systems. Those capture the generators' waste heat as well as their electricity, and that heat goes back into the building — heating water, maintaining the digesters, warming growing areas, supporting food processing.

Waste becomes input

This is the fundamental idea: waste from one part of the system is a resource for another.

Crop residues become animal feed or digester material. Manure becomes biogas and fertiliser. Digestate is processed to recover nitrogen, phosphorus, and potassium for the crops. Food-processing waste enters the same system instead of a landfill.

Water

Water works the same way. Rainwater is collected and stored. Water leaving agricultural systems is treated and reused where appropriate. Condensate from air conditioning provides another recovered source. Different levels of treatment mean the building never spends drinking-quality water on jobs that don't need it. Aquaculture integrates through aquaponics, with plants stripping nutrients from the fish water.

Energy

The energy system draws on several sources rather than one: solar across the roof and suitable façades, possibly wind or engineered airflow at the upper levels, batteries for short-term fluctuation, thermal storage for heat, and biogas for dispatchable power when solar and wind fall short.

The building should not try to disconnect from the grid. Connecting makes it more practical, not less — export when renewable generation exceeds demand, draw when it falls short. The objective is to be an efficient participant in the energy system, not to pretend it never needs outside resources.

What leaves the building

This may matter more than the energy generation.

Modern industrial systems treat waste as something to remove as quickly as possible. The vertical ecosystem takes the opposite approach: before anything is released, the system asks whether it can be prevented, recovered, reused, converted, or safely destroyed.

Methane is the example. Reducing production through feed and management is better than capturing it later. If it can be economically recovered, it becomes fuel. If a dilute stream cannot be recovered economically, controlled oxidation is preferable to venting it.

The same logic applies elsewhere. Ammonia from livestock contains nitrogen, which agriculture needs. Hydrogen sulphide contains sulphur. Carbon dioxide is what the plants are for. None of these should be assumed to be waste before asking whether there is a useful destination.

Not everything can be turned into something valuable. Some materials must be treated, destroyed, or neutralised — and combustion creates its own pollutants, so burning a waste stream is not automatically a solution. The treatment system has to be judged on what comes out of it. The goal is to keep uncontrolled emissions to a minimum and ensure anything released has been properly treated.

A district instead of a tower

The most interesting possibility may not be a single building. Several agricultural towers could operate as a connected district — one specialising in crops, another in livestock, another in aquaculture, another in processing and resource recovery — trading electricity, heat, water, carbon dioxide, biogas, and fertiliser between them. What begins as one building becomes an urban agricultural ecosystem.

The simple version

The building would still need outside inputs. Seeds, equipment, minerals, replacement parts. Closing every loop completely would be neither practical nor economical. The goal is to dramatically reduce the waste, energy, and imported resources needed to produce food.

But the underlying idea is simple. Instead of designing buildings that consume resources and send waste away, we could design them to continuously look for connections between what they produce and what they need.

A cow produces manure. The manure can produce biogas and fertiliser. Crops need fertiliser. The biogas can produce electricity and heat. The crops need heat and electricity. Plants consume carbon dioxide. Animals and people produce carbon dioxide. Water can be collected, treated, and used again.

The building stops being a collection of separate systems and starts behaving like a living one.

That is the vision of the vertical ecosystem: a building where the waste of one process becomes the fuel, food, water, or raw material for another.

Open problems

These are the parts I haven't worked out. If you know something about any of them, I'd like to hear it.

1. Dilute methane from livestock ventilation. Membrane separation works well on concentrated biogas, but barn air is methane at trace concentrations in a very large airflow. Different problem, orders of magnitude harder. Controlled oxidation may be the only realistic answer.
2. Membrane durability in this environment. The membrane literature flags fouling, plasticisation, and ageing — particularly in the presence of hydrogen sulphide and ammonia. A livestock building produces both.
3. Structural cost of livestock. At what point does the weight, feed, water, and ventilation load stop being worth it? Should the livestock component be a low-rise building attached to the tower rather than inside it?
4. Feed. If feed has to be trucked in, much of the efficiency argument weakens. How much could realistically be grown in the building?
5. Economics. Every closed loop costs something to close. Which ones pay for themselves, which need support, and which should be left open?
6. Tower or district? Splitting functions across connected buildings might solve several problems at once — or add complexity and transport losses.

References

[1] Masad Mezher Hasan, José Francisco González Álvarez, Jinsoo Kim, Mohd Roslee Othman, "Biomethane purification from biogas by methane selective membrane: Effects of different biofuel grades on electricity generation from natural gas turbine," Process Safety and Environmental Protection, Volume 198, 2025, 107161. ISSN 0957-5820. https://doi.org/10.1016/j.psep.2025.107161

Note: figures above are from the paper's abstract; the full text is paywalled. The study is lab-scale.