As a company that supplies a wide variety of power units for customers all around the world, Honda has been electrifying its mobility products such as cars and motorcycles while also increasing the efficiency of it power units, targeting the realization of carbon neutrality.
In addition, Honda is researching and developing technologies to capture CO2 from the atmosphere and convert it into carbon-neutral fuels.
One of the things we decided to explore is the great potential of algae, which have existed on the earth since prehistoric times some approximately 3 billion years ago.
In order to increase the efficiency of the carbon cycle, Honda is exploring the utilization of algae, which has great potential as a renewable resource.
Honda aims to realize carbon neutrality for all products and corporate activities Honda is involved in by 2050.
To achieve carbon neutrality, it is important not to increase the concentration of CO2 in the atmosphere by reducing the use of fossil resources and efficiently using renewable resources. Currently, however, we do not have a society in which all social activities, including mobility, can be covered by renewable energy, and the situation differs from country to country and from region to region. To address these challenges, Honda is researching and developing a wide variety of technologies which will enable circulation of energy with three cycles – electricity, hydrogen and carbon cycles – and optimization of energy use depending on the applications and country/region.
Specifically, we are envisioning the use of solar-derived and other forms of electricity for short-distance mobility products, and the use of hydrogen made from renewable electricity for long-distance, heavy-duty trucks and other vehicles. For high-powered aircraft and ships, which are difficult to electrify, we are envisioning the circulation of energy through the carbon cycle, using renewable fuels converted from atmospheric CO2. Honda will pursue carbon neutrality by applying the right technologies for the right purposes.
Honda has been researching biofuels including bioethanol. In order to increase the efficiency of the carbon cycle, among various research subjects, we decided to pursue research on algae, which has great potential as a renewable resource. Currently, we are continuing this research with an eye to utilizing algae for a broad range of applications, including biofuel for aircraft.
As long as there are sunlight, water and nutrients such as nitrogen and phosphorus, algae absorb CO2 through photosynthesis, proliferate through cell divisions and produce valuable components such as carbohydrates and proteins. Carbohydrates can be used to produce bioplastic as well as biofuel, while proteins can be used to produce food, cosmetics, pharmaceuticals and other products.
Another noteworthy advantage is that algae can be cultivated even in areas not suitable for agriculture, such as desert environments and areas that suffer from salt damage. That means algae do not compete with food production, which is an issue in the production of biofuels made from agricultural crops such as sugarcane and corn.
Algae have potential to reduce the concentration of CO2 in the atmosphere as well as to solve issues facing humanity such as energy, environment and food issues. Honda wants to contribute to the wellbeing of people with this original technology.
Striving for mass cultivation,
which is considered difficult,
Honda created algae that can be survive and growth in difficult environments.
Algae are broadly classified into two groups - large seaweeds such as wakame (brown) seaweed and sea kelp, and small microalgae with the size of 10 to 100 microns. Honda DREAMO is a mutation of a type of microalgae called Chlamydomonas, and it is an alga for which Honda newly obtained a biological patent.
Mass cultivation of microalgae is considered difficult. Although they can be cultivated in a sterile and temperature-controlled environment such as a laboratory, when they are cultivated outdoors for photosynthesis with natural sunlight, the growth rate of the algae decreases due to predation and deprivation of nutrients caused by contamination*. In other words, overcoming the issue of contamination will be a foothold for mass cultivation. Therefore, rather than trying to eliminate contamination, Honda worked to develop "strong algae" that could tolerate contamination. More specifically, we cultivated strains of Chlamydomonas in the presence of contamination, then picked up the survivors. By repeating this screening process, we bred Honda DREAMO, which grows fast and is less susceptible to contamination.
*Bacteria and insects that contaminate the culture fluid.
As mentioned above, Honda DREAMO's greatest feature is its resistance to contamination. The common method used to protect algae from contamination is to destroy the contaminants by adjusting the pH of the culture fluid. Honda DREAMO does not reduce its growth rate while coexisting with contamination. It has been confirmed that Honda DREAMO undergoes cell division at a rate of approximately once every five hours and grows up to 32 times per day. As a result of repeated screening in a low-temperature environment, Honda DREAMO has also acquired low-temperature resistant characteristics.
Combined with the characteristics of algae that can be cultivated anywhere as long as there is sunlight and water, the characteristics of Honda DREAMO make it possible to cultivate and utilize this algae in more regions around the world.
Another key feature of Honda DREAMO is that its composition can be easily adjusted to realize the optimal composition ratios to use it as a raw material for various products. Algae contains carbohydrates, proteins, lipids, vitamins and other elements. For example, a higher ratio of carbohydrates is better for ethanol production, while a higher ratio of proteins is more efficient for food production. The composition ratios can be changed to have 60% carbohydrates or 69% proteins in just 3 days, allowing Honda DREAMO to be used to produce what is needed when it is needed.
In addition, microalgae are generally covered with thick cell walls, so the cell walls must be dissolved or destroyed in the process of making ethanol. In contrast, Honda DREAMO has very thin cell walls, making it possible to convert starch into glucose simply by adding enzymes such as α-amylase and glucoamylase without destroying the cell walls. This feature of Honda DREAMO enables the simplification of the ethanol formation process and thus increases efficiency of ethanol production.
What is the Honda DREAMO System that achieves excellent production efficiency and absorbs a large volume of CO2 while reducing energy consumption?
The cultivation system is also important for outdoor algae cultivation. Pool-type systems are easy to scale up and cost-effective, but they are difficult to control contamination. They also require shallow water depths to allow sunlight to penetrate to the bottom of the pool, which makes it easy for CO2 added to the water to escape into the atmosphere.
In contrast, the flat panel system, in which multiple units of algae and culture fluid are enclosed in a thin panel, is more expensive than the pool system, but it is more efficient and has been increasingly used in recent years. Honda adopted this flat panel system and developed the Honda DREAMO System, which significantly increased the amount of CO2 absorbed by the algae while keeping costs as low as possible. The DREAMO System achieves excellent production efficiency.
The Honda DREAMO System is a flat panel system measuring 1.8 meters wide, 0.9 meters high, and 0.2 meters deep. It has a tiltable structure that enables changing panel angles so that sunlight can efficiently enter the system while being used in various regions at various latitudes.
Due to their structural design, flat-panel systems often face a challenge that algae tend to sink to the bottom. Honda DREAMO System addressed this issue by injecting CO2 from the bottom of the panel along the guides, which makes CO2 circulate like a flowing pool while agitating the algae. This increases the contact rate between the CO2 and the algae and ensures uniform solar irradiation of the algae.
Moreover, the Honda DREAMO System adopts a heat-insulating structure that features a water layer around the culture layer to increase the thermal mass of the water. This insulation structure enables the system to maintain appropriate water temperature and makes cultivation of algae possible even during the winter in Tochigi, Japan, when outdoor temperatures can reach -5℃ (23℉). A common temperature control equipment can maintain the optimum temperature for cultivation, but such equipment emits CO2 through the use of energy such as electricity. The Honda DREAMO System enables more CO2 absorption while minimizing energy consumption.
For the purpose of producing fuels such as ethanol, it is necessary to lower the concentration of nitrogen and sulfur in the culture fluid to increase the carbohydrates (starch) in the composition of the algae; however, this will reduce the growth rate of the algae. In general, therefore, it is necessary to cultivate the algae first in the culture fluid with the right mix of elements for growth, and then cultivate again after reducing the nitrogen and sulfur concentrations in the fluid.
In contrast, Honda has succeeded in increasing the ratio of carbohydrates while maintaining algae production volume by precisely adjusting the concentration of each element in the culture fluid. Furthermore, Honda has pursued a low-energy cultivation process and has made it possible to recycle 100% of the culture fluid without sterilization or other treatment. Recycling the culture fluid without sterilization normally makes it easier for contamination to proliferate, resulting in lower production volume of typical microalgae; however, Honda DREAMO, with its strong resistance to contamination, is practically unaffected. This characteristic and the precise adjustment of the concentration of each element in the culture fluid enabled the culture fluid to recycle 12 times, instead of the usual limit of two or three times, by simply replenishing water and the elements consumed as nutrients. This enabled 84 consecutive days of continuous cultivation of Honda DREAMO. The ability to recycle the culture fluid many times minimizes the amount of elements and water used, making the system extremely eco-friendly.
In the Honda DREAMO project, team members with biotechnology backgrounds are in the minority. Team members come from various fields such as mobility-related design, analysis and production equipment development. That is why we are working without being bound by the common sense of algae or biotechnology. We push beyond what are considered to be the limits based on common knowledge in the industry. We are capable of designing and creating our own experimental facilities, conduct experiments immediately, and build our own production facilities. Honda DREAMO was born as a result of repeated trial and error and a persistent state of challenge. Knowledge and experience that seem completely unrelated to algae come to life. The ability to create this kind of project environment is also one of Honda's strengths.
Honda DREAMO will undergo an extended verification on a greater scale, including LCA (Life Cycle Assessment)* and evaluation of durability, reliability and the possibility of cost reduction. Moreover, we will conduct verification tests at Honda production plants in Southeast Asia and in Japan by supplying CO2 emitted from boilers in use at production plants to the algae cultivation facilities. Through these verification testing, we will continue working toward the practical application of Honda DREAMO technologies.
Furthermore, in order to deliver the algae we harvest to our customers in the form of various products, we will start conducting verification while viewing our algae as the raw material of foodstuffs and plastics. Due to the high cost of cultivation, products made from algae are currently limited to expensive cosmetics and some functional foods for health promotion. In addition to the fact that typical microalgae have low resistance to contamination, the impact of atmospheric temperature changes experienced throughout the year in regions with four seasons, such as Japan, make it very difficult to cultivate algae outdoors. Therefore, algae are being cultivated indoors in a sterile environment with controlled temperatures. For such indoor algae cultivation, a heterotrophic method based on organic carbon sources such as sugar is often used, rather than photosynthesis that absorbs CO2. This type of cultivation is expensive and consumes a large amount of energy.
For Honda DREAMO, we have established a low-energy outdoor cultivation process that maximizes the use of sunlight, thus reducing cost. One of the key features of algae is that we can use up all of the components. By taking advantage of this characteristic, we are envisioning to make it a viable business by producing low-priced fuels and plastics, while at the same time producing high-priced pharmaceuticals, cosmetics and health foods using the by-products.
Honda DREAMO has the potential to contribute to resolving various problems facing humanity, such as environmental issues through CO2 absorption and bioplastics production, energy issues through biofuels, and food issues through protein-based food products and livestock feed. Honda will accelerate its efforts to deliver products that benefit as many people as possible.
*A method for quantitatively evaluating the environmental impact of all processes from the extraction of raw materials necessary for products and services to the use and disposal of products.
■All measurements included in this story were conducted internally by Honda.