Part of this year's RebelBio cohort in Cork, NuLeaf Tech uses biochemical and ecological biomimicry to turn wastewater into a resource, using engineered wetlands, microbial fuel cells and vertical farming. Rachel Major and Ari Ochoa report

CLICK TO ENLARGE Fig 1: Breakdown of water availability on Earth (NuLeaf Tech)

Where there is water there is life. And yet, less than 1% of the world’s water is unpolluted and accessible freshwater for human use (Fig.1). The .01% of surface freshwater, which is most readily available to us, is too small to even be seen on a graph. We share this sliver of water with all life on the planet that requires freshwater.

Coupled with an exponentially growing human population, these factors make water scarcity an escalating problem. According to the United Nations, some 50% of the world will experience water scarcity by 2030. Without addressing the world’s wasteful water infrastructure, these numbers will continue to climb. From off-grid living to urban life, wastewater treatment technology is outdated. The largest issue is that current technology treats and releases water, rather than reusing or recycling this precious resource.

This is a problem for rural homes and the on-the-rise tiny house and container-home communities. In these situations, septic tanks are the most common option. They can cost $10,000 (~€8,500) to install and they simply let the waste sit until the tank can be cleaned out – for a fee. In these isolated homes and communities, every resource is valuable, but water – an absolute necessity – is not wisely used.

Wasteful water infrastructure

CLICK TO ENLARGE Fig 2: An aerial view of a traditional wastewater treatment plant (

Irresponsible water usage may seem, like these rural communities, isolated, but wasteful water infrastructure is also a problem in more densely populated areas. Most water used in urban areas is sent to treatment plants, which usually rely on old technology with many limitations. In addition to only treating and releasing water, municipal treatment plants (Fig. 2) are expensive, huge and often cannot meet industrial needs.

These plants can cost millions in construction, with significant annual operation and maintenance costs. As much as 50% of these operation costs lie in the energy needed to power the plant. At around 0.5 km2, these plants can be impractically large, especially since cities often need multiples of such facilities. Lastly, they are typically designed only for municipal waste and are unable to cope with higher strength wastewater sources, like agriculture or industry.

CLICK TO ENLARGE Fig 3: A schematic of a subsurface flow constructed wetland (

A newer option for off-grid, municipal and industrial waste treatment are reed beds or constructed wetlands (Fig. 3). These are artificial ecosystems that utilise wetland plants and microbes to clean a wide variety of waste. They are 1/20th the cost of conventional plants, require minimal maintenance and can typically treat waste without producing foul odour.

However, they still do not address the need to recycle, as they only treat and release water. They are also incredibly land intensive, like traditional wastewater-treatment plants.

By 2060, it is estimated that 60% of the world’s population will live in cities. Wastewater technology in these highly populated areas must become compact, cost-effective and industry adaptable with the ability to recycle water. An alternative to this challenge is to make off-grid living affordable and comfortable. This means not sacrificing the modern high-tech lifestyle to which many people are accustomed, while providing them with the means to obtain resources they need such as water, energy and food.

This pressing challenge requires an inherent shift in the way we think about waste. Water needs to be reused and recycled and, for maximum resource efficiency, the nutrients in waste must be unlocked. The good news? The solutions to these problems are right outside our window.

Biomimicry learns from nature for technological innovation. It leverages 3.8 billion years of research and development to solve the world’s greatest challenges. For nearly every problem that humanity faces, nature has an answer.

The mental shift of working with nature, instead of over it, creates technologies that are truly sustainable – from the materials they are made from, to how they work. The wealth of untapped solutions in the natural world offers a novel approach to problem solving for a new era of smarter, more efficient technology. By looking through Mother Nature’s lens, biomimicry can revolutionise humanity’s relationship between nature and technology for the betterment of all.

Biochemical and ecological biomimicry

CLICK TO ENLARGE Fig 4: Overview of NuLeaf’s input and output values (image: NuLeaf Tech)

NuLeaf Tech, a biomimicry company, starts with creating solutions for water by learning from the Earth’s nutrient recycling processes. Our combination of biochemical and ecological biomimicry naturally and economically turns waste into a resource.

In nature, waste does not exist for long because everything is recycled and reutilised in some way. To model these nutrient processes, NuLeaf marries three complementary technologies. This takes wastewater as an input and creates outputs of reusable water, energy and crops (Fig. 4). These technologies are engineered wetlands (EWs), microbial fuel cells (MFCs) and vertical farming.

EWs are NuLeaf’s improved version of constructed wetlands. Invented in the 1950s, constructed wetlands have been used to clean agricultural, food and beverage, and municipal waste. They also have additional applications in bioremediation.

They are capable of removing toxic pollutants, such as heavy metals and organic hydrocarbons, as well as transforming nitrogenous and phosphorus waste into liquid fertiliser. This process treats soluble and solid waste. On average, they are 0.6 km2 in size, but some are so large that they double as wildlife sanctuaries. NuLeaf’s EWs harness the cleaning power of these systems, but package the wetland into a compact unit. Our first system is 2m3 in size and hexagonal in shape, allowing for easy expansion as modular units.

Fig 5. Overview of a simple MFC (

MFCs (Fig. 5), the second technology implemented in our system, generates electricity by utilising microbial digestive processes. As microbes metabolise organic waste, electrons as well as energy-rich molecules like hydrogen and methane are released. These electrochemical reactions also generate pure water while breaking down simple organic waste.

MFC technology originated in the 1930s and has been used for applications in water purification, desalination and energy generation. Their current generated is relatively small, about 300mA for a 15 cm3 cell, but by linking several together they are capable of powering lights and small pumps. Within the last five years, research into the type of electrodes and their orientation in the cell has increased power output to make these fuel cells commercially viable.

MFCs and EWs are complementary technologies for two reasons. The first is that the microbes in these fuel cells are naturally occurring in wetlands around the world. The second is that MFCs cannot break down complex organic waste, but waste that has passed through the wetlands is simple enough to be digestible. Strangely enough, though, these technologies were only first coupled together in research settings in 2016.

NuLeaf brings these technologies together in a commercial setting. In addition to the aforementioned benefits, NuLeaf links several MFCs together to make our system self-powered. The MFCs provide an additional step of waste breakdown after the EWs to make our water even cleaner. Additionally, many MFCs burn any methane created to get energy from combustion of biogas. NuLeaf harnesses the flow of electrons directly to store electricity in a battery, so our energy source is combustion-free.

Vertical farming and hydroponics

CLICK TO ENLARGE Fig 6: Artist’s rendition of the NuTree (NuLeaf Tech)

The third technology implemented in our system is vertical farming. Evidence dates vertical farming to prehistoric times but, within the last century, pressure to make agriculture more space-conscious has made it a science. Specifically, NuLeaf makes use of vertical hydroponic farming.

Hydroponics is the method of growing crops in water without a soil medium. EWs transform nitrogen and phosphorous waste into liquid fertiliser that plants can use as nutrients. As the plants uptake the nutrients and grow, the water in our system is cleaned further.

Our first product, the NuTree (Fig. 6), is the first commercially available option that joins these three technologies. The result is a compact, self-powered and modular unit that recycles wastewater to create reusable water and crops. Future goals are to create drinkable water by combining the pure water from the MFCs and diluted water from the EWs/hydroponics. Making the system energy positive rather than energy neutral is another long-term goal.

CLICK TO ENLARGE Fig 7: NuLeaf’s proof of concept consisting of engineered wetland and hydroponic polytunnels (NuLeaf Tech)

A single NuTree unit can completely treat thousands of litres per day by treating both solid and soluble waste without giving off any odour. This is enough to treat the daily water used by a household but, because our units are modular, they can be expanded for industry use. The technology is both eco-friendly and efficient, as it implements microbes and plants to recycle water and produce crops.

Unlocking nature’s secrets has been a long journey for NuLeaf. We started in 2015 when our CEO brought the idea of bridging sustainability and biomimicry to NASA Ames. Nearly 150 people applied to be a part of the team. We quickly became an independent educational/DIY organisation and eventually the start-up known as NuLeaf Tech Inc in March 2017.

Shortly after, we were accepted to the RebelBio accelerator program in Cork and received $100,000 in funding. We have filed a provisional patent, built a horizontal proof of concept (Figs. 7and 8) and won a Stanford Research Award.

Wineries and breweries

CLICK TO ENLARGE Fig 8: NuLeaf’s microbial fuel cell (NuLeaf Tech)

We have received Letters of Support from the #1 winery in the US, Ridge Vineyards, and the award-winning brewpub Rising Sons. We were accepted to attend Hello Tomorrow and will be presenting at the World Water Tech North America Summit.

Our entry market is craft breweries and wineries in California, where we are based. Wastewater treatment is an inherent and costly part of running these business. California is world-famous for its craft beer and wine and has some of the most expensive and strictest water regulations. Every industry and every household uses water, so future applications of our flexible and modular system are quite broad. They include food, beverage, agricultural, aquaculture, municipalities and developing nations.

We will be returning to the Bay Area in November. Within the next six months, our scientific goals are to build a 2m3 vertical NuTree prototype and a miniature NuTree for industrial and residential use, respectively. In the beginning of 2018, we will launch a kickstarter followed by a equity fundraising round.

NuLeaf as a company fosters sustainable lifestyles through resource independence by promoting individual, community and global shifts in technologies. We are inspired by the wonders of the natural world to help create a high-tech and sustainable future accelerated by nature’s solutions. If you are interested in following our journey, follow us on Twitter and Facebook. Please join us as we turn a NuLeaf in tech!

CEO Rachel Major has degrees in chemistry, biology and management. She has worked in engineering and geochemical labs and at the world’s leading biomimetic consultancy. CTO Ari Ochoa has a biochemistry degree and is a self-taught microbiologist with a lifetime’s knowledge of construction and wetland chemistry. Together, they leverage a creative and interdisciplinary mixture of eco-friendly and high-tech skills. They are passionate about leveraging bioinspired design to revolutionise humanity’s relationship between nature and tech for the betterment of all. Anne CarriganChemenergy,sustainability,wastewater,water
Where there is water there is life. And yet, less than 1% of the world’s water is unpolluted and accessible freshwater for human use (Fig.1). The .01% of surface freshwater, which is most readily available to us, is too small to even be seen on a graph. We share...