Advanced photobioreactors can now outperform modern agriculture. How can they be expanded to make agricultural production carbon-negative?



It is now within the limits of current technology and photosynthetic biology to build a cost-effective, scalable indoor photobioreactor system that can efficiently accelerate the production of algal biomass for nutritional and agricultural consumption. This technology has immediate commercial application, but several environmental advantages are also inherent to the system, including more efficient water and land use and a relatively smaller carbon footprint. Widespread deployment of this technology in conjunction with renewable energy sources and/or carbon sequestration could potentially extend the impact to be carbon negative.  

In many ways, the carbon challenge is a result of an imbalance between:

            Photosynthesis (conversion of light, carbon and water into stored biochemical energy)

            6CO2 + 6H2O + light --> C6H12O6 + 6O2


            Respiration (the conversion of stored biochemical energy into other forms)

            C6H12O6 + 6O2 --> 6CO2 + 6H2O + energy

Many of the problems we face today are due to the fact that one half of this cycle has been aggressively industrialized, while agricultural systems remain limited by their vegetative photosynthetic capabilities. Even modern increases in overall productivity are ultimately achieved on the back of a fossil fuel economy. 

Recent photobioreactor advances draw on breakthroughs in materials science, advanced manufacturing, light sources and automation, in addition to recent insights in biophysics, to increase the efficiency of photosynthesis itself. Reductions in energy, labor and water efficiency already make this approach less carbon intensive than most industrial agriculture.

Powering this improved photosynthesis technology with renewable energy sources could potentially extend the impact of both technologies, even making it possible to achieve carbon negative agricultural production.

What are the key outcomes and impact of your solution?

In order to understand the potential global carbon impact of the photobioreactor technology, it's helpful to compare it to existing agricultural production.

Current Agriculture

In 2014, global production of the top four agricultural commodities (corn, wheat, rice and soy) reached 2.6 billion metric tons of biomass, using over 14 million km^2 of land and producing 2.85 billion tons of CO2. On their own, these four crops are estimated to account for >60% of the calories we eat, 28% of the land we farm and 26% of the CO2 we emit as a species.

Photobioreactor System

One high-density cluster of photobioreactors – deployed as a stand-alone module similar in size and shape to a modern grain silo – would require a 60 m^2 footprint and 125-250kW / year of energy, while producing 43.8 metric tons of biomass annually.

If just 20% of the world’s four main crops were replaced with biomass produced using currently or soon-to-be available technology for high-density photosynthetic bioreactors, powered by wind and nuclear power:

  • The direct carbon absorption of the full system could be between 221 and 351 million metric tons.
  • The carbon offset from the agriculture they displaced could be an additional 570 million metric tons.
  • Over 2.75 million km^2 of land (an area 2/3 the size of the United States) could be potentially repurposed.


This adds up to a potential total CO2 offset of 922 million metric tons - almost 10% of all human global emissions in 2015, greater than what would be saved if everyone on the planet gave up driving without the associated sacrifices.

These estimates are obviously very different depending on the power source although they also do not account for additional system efficiencies and benefits either - e.g., that the biomass of these systems can be run on salt, grey and wastewater; that the system would be inherently NPK-negative; or that it can produce a superior biomass with significantly less waste (i.e., more kernel with less cob).

What is clear is the carbon reduction potential that exists, and the importance of considering the impact of expanding this technology.

What actions do you propose to realize your stated goals?

While the theoretical potential for bioreactor-driven biomass production from algae and cyanobacteria to exceed current agricultural productivity is well-established, there are other important design considerations that must also be considered: 

·       Indoor Production. Isolating the growth environment from the ambient environment removes the effects of the sun’s location and seasonal variations, making it possible to grow 24 hours a day, year-round. A substantially closed-loop system is also better insulated from parasites, poor weather and other typical challenges for outdoor agriculture. Disconnecting the growth environment from the ambient environment also allows for better control of inputs and outputs, as well as reduced risk for environmental contamination when using genetically enhanced organisms.

·       Multi-Level High-Density Capability. The bioreactors should ideally be modular, scalable and capable of being configured vertically (stacked) as well as horizontally, exponentially reducing the amount of land required to produce comparable amounts of biomass using current methods. In this way, one square meter can be come 10 square meters of illuminated surface, and 175kg/year can become 1.75 metric tons/year without expanding outside the original square meter footprint.

·       Low-Impact, High-Efficiency Components. The system should feature design and materials that are relatively low-energy, low-cost and capable of using low-impact sources of water, such as inexpensively sterilized salt water. Energy and labor efficiency are also critical, as is the source of the energy from a carbon perspective. Automation, high-efficiency lighting and advanced materials and manufacturing also play an important role.

A photosynthetic system that is independent of sunlight and insulated from its environment facilitates a wide range of design options, enabling system variations that can be adapted to many climates and geographies. Allowing for a wide range of potential host organisms also increases the system’s flexibility, enabling it to produce a wide range of potential end products while adapting to the resources available in a given environment.

The importance of this adaptability is not only key to the system’s ability to operate effectively across different products and regions, but also of primary importance in a world where local climates are becoming increasingly unpredictable and chaotic.

While there are immediate commercial advantages to this approach that are already being pursued, our proposal is to explore ways that this technology can be further leveraged to meet additional goals such as reduction of carbon and other waste. We have identified three immediate routes for exploration:

·      Renewable Power and/or Co-Location. In an ideal world, where renewable energy sources make up the majority of power on a majority of smarter grids, the need for co-location is unnecessary. In the near term, however, an indoor and land-efficient system could be co-located with a variety of renewable energy sources. As this graph shows, there is a drastic difference in CO2/kWh produced between nuclear, wind and all other forms of power. If true carbon negativity is the goal, wind and nuclear would be the most suitable power sources.

·       CO2 Sequestration. Because the system ultimately relies on carbon as its primary production input, there are numerous potential scenarios in which co-locating with concentrated CO2 producers could be beneficial to all parties. The more concentrated, cleaner CO2 resulting from industrial fermentation, food production and natural gas power can be used in photosynthetic systems to produce certain high-value biogenics, to control system pH, and as a more concentrated carbon source for those organisms that prefer it to atmospheric carbon alone.

·       Wastewater Treatment. Modern wastewater treatment facilities discharge waste Nitrogen, Phosphorous and Potassium (collectively “NPK”), a runoff that leads to eutrophication in the form of massive and destructive algal blooms. It has been shown that photobioreactor systems can rely on a variety of NPK sources, including blends of organically and inorganically derived fertilizers. Many of them are also NPK scavengers, which will absorb virtually all of the bioavailable nutrients in their environment before entering dormancy or life-cycle stages not dependent on available NPK. By using the photobioreactor systems as environmental buffers, we can prevent the runoff from entering the environment, mitigating the occurrence and impact of algal blooms while making efficient use of wastewater sources.

While each of these potential integrations could have major carbon impacts at scale, it is necessary to understand the specific design and engineering requirements of integration with the processes above in order to both maximize the environmental impact and preserve the commercial economics of the biomass production business.   

The modular design of the core system is essential to both its photosynthetic effectiveness, balancing the organism’s environmental needs with cost and labor requirements, and to its utility as a distributed tool to address excess carbon. While the initial system is conceived as a large factory facility, scaling up to include several subdivisions of modules, it will achieve its greatest impact in terms of carbon reduction and efficient use of resources when expanded as a distributed model and integrated as described above.


Aside from the types of challenges inherent to developing and scaling any new technology, the primary challenge is the classic “chicken and egg” dilemma: integration for environmental benefit is a secondary priority for everyone and, in the absence of either economic or regulatory imperatives, unlikely to be commercially prioritized. As with any sort of technology adoption or integration, one major hurdle is the new technology’s ability to interact with incumbent systems. Adapting the technology for integration will require detailed engineering and design, but without a clear commercial driver, this is unlikely to be pursued.

·       Renewable energy producers are mostly focused on producing a commodity – electricity.  Although these producers are often active in pursuing other technology integrations such as big data, demand-side management and storage, there is not a strong imperative to look at photobioreactor-driven agriculture absent a specific opportunity or incentive.

·       The same is generally true for wastewater treatment facilities and producers of CO2, especially when they are generally regulated industries.

·       On the other side, integration for carbon reduction is also not a priority for many bioreactor-driven biomass production businesses. These businesses are generally privately funded and, while often more carbon efficient than industrial agriculture, are also not incentivized to pursue these additional integrations outside of their core mission of producing cost-effective products.

Who will take these actions?

The photobioreactor designs and technology described herein are already being made for deployment in our current economic and regulatory environment, funded and supported with private investment, and driven by existing and projected consumer and market forces.

The key actors in renewable energy, wastewater and other carbon producing industries are largely similar. While it’s always possible to incentivize these collaborations through regulation, or create other more general market incentives such as a carbon tax, our view is that these solutions will need to be conceived and designed to operate economically in the existing regulatory and economic ecosystem.

Addressing the integration issues detailed here will likely involve NGOs, governments or social investors who could provide the seed capital to sponsor the initial R&D, design and engineering tasks related specifically to the integration of the photobioreactor system with existing technologies, processes and systems.

Target geography

Target locations for this solution will primarily be areas where the supporting bioreactor infrastructure, renewable energy development and environmental impact are highest and intersect. 

One of the core strengths of the design principles for the photobioreactor system is deployability in multiple geographies. Peak efficiencies will most likely be reached in colder climates, but locations will be driven more by the end-use markets for the potential products and by access to qualified labor and technology markets than by the system’s requirements.

Distribution can also be prioritized by placing systems in areas of greatest concern in terms for CO2 and NPK output, allowing them to take up waste before it becomes diluted in the environment. For example, implementation focused on co-location with industrial fermentation and other agricultural sites can make more efficient use of waste CO2 and NPK runoff, while also making use of existing infrastructure in place for biomass utilization. Co-location near areas of high population (urban centers) offers similar opportunities.

What do you expect are the costs associated with piloting and implementing the solution, and what is your business model?

Since the opportunity being contemplated likely involves collaboration between two or more existing entities, with at least one likely being private, the bulk of the core technology development costs will have been separately financed within those respective businesses. We are only addressing the initial engineering and design questions related to the feasibility of the integration.

For this purpose, we are assuming (1) that each business is able to continue profitable production, operation and growth, whether it’s the biomass producer, renewable energy provider or wastewater treatment entity, and (2) that the funding required is only to establish feasibility, explore long-term scaling and sustainability options, and initiate steps toward the technology integration.

The cost for these sorts of feasibility studies is also highly variable, but will generally fall in between $250,000 and $1 million. These funds would likely be from a mix of public and private sources, including:

1. The companies themselves, contributing both time and materials;

2. Outside NGOs;

3. Government grants (such as those related to water quality, etc.); and

4. Social Investors.

The NGO and government entities in this process act as a catalyst, providing initial funding to prime the pump for the additional investment.


Related solutions


Gordon, Jeffrey M., and Polle, Juergen E. W. Ultrahigh bioproductivity from algae. Applied Microbiology & Biotechnology (2007) 76:969-975. 24 July 2007.

Sayre, Richard. Microalgae: The Potential for Carbon Capture. BioScience (2010) 60 (9): 722-727. 01 October 2010.

US Environmental Protection Agency eGRID2006 Version 2.1, April 2007

US Department of Energy, Energy Information Administration – Average Retail Price for Bundled and Unbundled Customers by Sector, Census Division and State, 2005.

The World Bank DataBank 

Oxfam International. “Feeding Climate Change.” ISBN 978-0-85598-750-3. June 2016.

Food and Agriculture Organization (FAO) of the United Nations. 

Nuclear Energy Institute (NEI):

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Solution Summary
Expanding the Role of Industrial Photosynthesis in Carbon Reduction
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