Originally published on EVObsession.
In my previous article I wrote extensively about a specific scheme in the United Kingdom for producing biogas, which would make the UK self-sufficient for domestic gas without the use of prime agricultural land or food crops. Writing that article piqued my interest in biofuels in general, and the legitimacy, or otherwise, of any objections and any specific advantages in the use of biofuels. In this article, I intend to write more about all kinds of biofuels, and why they might be necessary.
Biofuels can be classified into four types:
- Solid fuels for domestic heating, and for industrial processes, such as firing boilers for electrical generation, or other purposes.
- Biodiesel, meaning any plant oil that can be burnt in a diesel engine.
- Bioethanol, which is just alcohol and can be used as a substitute for petroleum and other volatile liquid fuels, or blended with biodiesel to make less dense fuel-oils.
- Biogas, which is just methane and is identical to so-called “natural” gas from fossil-fuel sources, which is supplied on the national gas grid for domestic heating and cooking, and for industrial users. It can also be used like LPG (Liquid Petroleum Gas) for powering motor vehicles.
What are the Objections to Biofuels?
The burning of any fuel will produce CO2, but also possibly pollution in the form of particulates, nitrogen oxides, sulphur dioxide, and carbon monoxide, although the extent of these depends on the nature of the particular fuel and the efficiency with which the fuel is burnt.
Even an efficient combustion will produce CO2, where we are trying to reduce CO2 in the atmosphere. The difference between CO2 produced by biofuels and CO2 produced by fossil-fuels, is that the CO2 from those fossil-fuels is being introduced into our current atmosphere, where it has never been before, or should we say, not for millions of years. The CO2 from biofuels is being reintroduced into our atmosphere from which it was extracted only a short while before. How long before depends on the type of material used to create the fuel. When wood is being burnt, the CO2 released might have been absorbed into the tree anywhere from 1,000 to 25 years ago, and will take time to be reabsorbed. That fact does count against the use of wood for fuel, although people would argue that trees absorb CO2 best when they are young and growing, so, by cutting down old trees and replacing them immediately with fresh new ones, the CO2 is being recycled, even if over a long period. It can also be said that no tree lasts forever, and dead trees will rot down, releasing carbon dioxide and methane as they do so. That being so, burning the wood is only releasing the CO2, which will be released eventually in any case, without the methane.
Where material is processed to produce ethanol or methane, that material can be from fast-growing plants, so that the period of recycling the CO2 is only a matter of weeks or months, and so is very much more clearly a recycling process. In cases where food waste and farm effluents are used as a feedstock for creating biofuels, if not used for that, they would simply be disposed of as waste. In that case, their breakdown would simply release the CO2 and methane directly into the atmosphere without any of the benefits of having used it as a fuel.
Another objection people have is that land and crops are being utilized for biofuel, which would otherwise be utilized for food. Again, this is a reasonable objection, but with careful management of resources it need not be a problem. It is easily solved by not using food crops, and by not using prime agricultural land. As explained in the article about biogas, this would be produced entirely without the use of food crops, using land that would otherwise be unproductive, provide rich wildlife habitats, and also would return rich natural fertilizer back to the land to improve it. In this way, agriculture would actually benefit, as would rural communities, from the increase in income and jobs that the biofuel industry would bring. If we can move away from rearing and eating bovine animals that each produce up to 500 Lts of methane everyday, the land they occupied could be used for biofuel feedstock crops.
Finally, it is definitely a problem where forests are cleared to create new land for planting crops for biofuels. Forests are essential to the process by which carbon dioxide is absorbed from the atmosphere, and oxygen added. It is imperative that forests should not be cleared in this way. It is also the case that, when such forest clearings are used for crops, the soil is rapidly depleted, and farmers move on to clear more forest, leaving a semi-desert behind. This criminal destruction of forests is something which should be prevented.
Such practices are especially prevalent in the production of palm oil, whether for biofuels or not. Oil is only suitable for diesel engines, and I will separately be explaining why diesel engines are a particular problem. We all know that diesel engines can produce higher levels of pollutants than most others, but do you know why? I will be explaining precisely why this is so. It is also the case that such problems can be largely eliminated, making diesel engines a more attractive option, if run on 100% biofuel.
There are also subsidiary objections concerning transport of biofuels and their feedstock. Transportation creates hidden CO2 output, especially where fossil fuels are used for the transport or in the processing. For example, the UK has replaced coal at some power stations with wooden fuel pellets, which are created in the USA and transported all the way across the Atlantic, representing much hidden carbon output.
A final objection is that providing people with biofuels instead of fossil fuels enables them to carry on as before, without adopting much more beneficial clean technology, such as induction hobs for cooking, heat pumps for space-heating, and electric vehicles for transport. Houses need to be built as carbon-neutral, with high levels of energy efficiency, rather than continuing to use gas to heat poorly insulated homes, or air conditioning to cool them.
What are the Benefits of Using Biofuels?
In an ideal world, people and their governments would not be sleepwalking towards planetary destruction. By now, all governments everywhere would be enacting legislation to shut down the fossil fuel industry, and to replace it with 100% renewable energy used in all-electric, energy-efficient homes, industries, and transport. The world is far from ideal, and world leaders waste their time and energy on petty international squabbles and wars, on unsustainable perpetual economic “growth,” and on the nonsense of petty nationalism, where global cooperation and unity is so much needed. Also, it appears some governments can be, or have been, “bought” by powerful financial interest groups and individuals, in order to represent their short term financial interests. In doing so, they compromise the long-term survival of the ecosystem we all rely on for our life to continue. Individual people, with a few exceptions, seem oblivious of the perilous consequences of their behavior, and continue their energy-extravagant, wasteful, throw-away lifestyles. They seem ambitious to have more of the same, rather than less. Car manufacturers, with a few exceptions, are still advertising their latest SUVs and sports saloons, with the emphasis on their sex-appeal and “vroom-vroom” qualities. The oil industry is just thrilled by the melting permafrost, as it can drill for yet more oil and gas in previously difficult and inaccessible places. It is a picture that engenders despair.
However, even if governments were wanting to change every car to an electric car, every medieval style of energy inefficient house to be exemplary in high-tech modernity and carbon neutrality, and every electricity generator to operate without burning fossil fuels, this could not be achieved in an afternoon. There would have to be a transitional period, where all the systems of energy production, management, and consumption would be transformed in a planned and orderly way. In the UK, in order to meet government targets for CO2 reduction, all fossil fuel gas burning for electricity generation and domestic heating must be ended by 2030. I am not sure that anyone has mentioned that to the current Tory government, as it is still promoting fracking for gas, and is busy replacing coal-fired power stations with gas-fired plants. I have not seen any schemes to replace all our fossil fuel gas supplies with biofuels, or plans to help home owners to convert to electric heat pumps for heating.
Where people have serviceable modern gas heating appliances for their home, and expensive motorcars sitting in their drive, they will be reluctant to immediately replace them with equally expensive heat pumps and electric vehicles. If we are to have all electric homes and transport, the infrastructure to generate and distribute all the required electrical energy will need to be in place. This would take time and huge amounts of money, as would the upgrading of homes to be anywhere near to carbon neutral.
As it is, progress is very slow, if not non-existent, and governments and corporations are largely perverse in their business-as-usual approach, while they talk much, but do little or nothing, or even work actively against progress being made. Any transition period, therefore, is likely to be extremely long, and during that period, it will be better for people to be burning biofuels than fossil fuels. Progress is so slow, in fact, that even a move towards using biofuels would be part of the transition itself, rather than something put in place up front, to enable a short transition period.
It could also be the case that in some processes and applications, it will prove difficult or impossible to replace a fuel-burning system with something operated entirely by renewable energy. There again, if we have to burn fuel, it would be better for that to be biofuel than fossil fuel.
Separate Types of Biofuels
It would not be reasonable to judge all biofuels as if they were one thing. If we consider, for example, the destruction of rainforests for palm oil plantations, where the palm oil is then used for creating biodiesel, that would be environmental vandalism. Compare that with the “gas from grass” scheme, which I wrote about in the previous article, which is a very well-planned, environmentally sensitive scheme, which would be of positive benefit to agriculture, wildlife, rural communities, and the national economy, while replacing 95% of gas from fossil-fuels with biogas for domestic use (in the UK). That scheme would allow people to continue using their gas-fired central heating boilers with much less detriment to the environment. It would also obviate the need for either importing gas, or obtaining gas locally through hydraulic fracturing of shale gas reserves, with its attendant destruction of rural areas and enormous risk to the water supplies.
Continuing to talk about biogas, the gas from grass scheme was only one possible source. Currently there is an enormous amount of food waste, farm waste, domestic waste, and sewage effluents, which are disposed of on a daily basis with little reference to the most environmentally beneficial method of disposal. For example, in the UK, much of the domestic waste used to be dumped into landfill sites. Over a period of years, the mountains of waste decompose, releasing carbon dioxide and methane into the atmosphere. Where the use of landfills has now been actively reduced, much domestic waste, including plastics, which could be recycled, are being incinerated, producing CO2 in addition to toxic gases. Farm waste and sewage effluent have been processed and used for fertilizer, but in the process and after application, CO2 and methane are released.
There could be a national effort to manage all kinds of waste, so that firstly, all that can be recycled is recycled, and secondly, all other waste is sent to anaerobic digester plants for the production of biogas. Only the residue would remain, which would make a good agricultural fertilizer and soil conditioner. In combination with the gas from grass scheme, this would supply all the gas requirements for both domestic and industrial uses, including electricity generation. Any surplus gas could be used for powering engines.
Hydrogen can also be considered as a biogas, and has the advantage of producing water vapor (H2O, or hydrogen oxide) when burnt, without CO2, (which is an end product of combustion of hydro-carbon fuels). Because it burns at a very high temperature, it can also produce oxides of nitrogen, sometimes called NOx, just like diesel engines do, which is an undesirable pollutant. Hydrogen used in a fuel cell to produce electricity is a very clean process, but the use of manufactured hydrogen is currently inefficient, as it takes more electrical energy to produce than it yields, and it would be better to use the energy directly. Hydrogen is the least dense substance there is, as it has only one proton and one electron in the atom. To carry sufficient hydrogen for use in a fuel cell in a vehicle requires a very high pressure gas bottle, and being highly flammable would be somewhat hazardous. Hydrogen gas stations are also very expensive, which is a further disadvantage. New systems are being developed, where fuel is stored as a hydrogen compound, such as ammonia, formic acid, or bio-ethylene, and the hydrogen extracted within the system before being fed into the fuel cell. This makes storage in the vehicle and at the refueling station much safer and cheaper.
Biofuels have to be assessed in conjunction with the systems in which they will be used, so looking at plant oils as a biofuel, the only option is for use in diesel engines, which no longer have a good reputation. The diesel engine was promoted at one time by governments as producing less CO2 per kilometer than a comparable petrol engine. It also used less fuel per kilometer, making it more economic. It has a high torque (the turning power in the drive shafts) at low engine revs and so is ideal for heavy transport and boats. However, what was not appreciated then was by how much more the diesel engine produced dangerous nitrogen oxides and particulates. As this has become more apparent as a problem, especially in cities, the diesel is now the big bad polluter to be shunned by all. So, why is the diesel engine more polluting? I assumed that it was because it ran on oil rather than petrol (gasoline), and my first thought was why not convert all these diesel engines to run on a “cleaner” fuel, but I discovered that the fuel is not the cause of the problem. The problem lies in the different ways the engines work.
In a petrol engine, the stages are:
- A piston travels down its cylinder, sucking a mixture of air and fuel into the cylinder from the inlet valve. (Or air from the inlet, mixed as it comes in, with fuel from the injector in a modern direct injection engine)
- The piston travels back up, the valves are closed, and the fuel, and air mixture is compressed, but not enough to ignite the fuel
- Just before the piston reaches the top, the spark plug ignites the compressed fuel, and air mixture. The piston, which has now gone past the top, and coming back down, is pushed down by the rapidly-expanding, hot combustion gases, much like a bullet in a gun barrel.
- The exhaust valve opens, the piston travels back up, and the exhaust gasses are pushed out.
In a diesel engine, the stages are:
- A piston travels down its cylinder, sucking just air into the cylinder from the inlet valve
- The piston travels back up, the valves are closed, and the air is compressed to be hot enough to ignite diesel fuel.
- Just before the piston reaches the top, the fuel injector begins to spray fuel into the very hot air, and it immediately starts to burn. The piston, which has now gone past the top, and coming back down, is pushed down by the rapidly expanding hot combustion gases, just as in the petrol engine.
- The exhaust valve opens, the piston travels back up, and the exhaust gasses are pushed out.
It is the high compression and temperature in a diesel that gives it its high efficiency and high torque at low revs. A diesel engine’s compression ratio is around 17:1. The “compression ratio” is the ratio of the full cylinder volume to the volume at the top of the piston travel. In a 2Lt 4-cylinder diesel engine, the full volume of each cylinder is 500 cc, where the final volume is only about 30 cc. In a petrol engine of the same size, the final volume is around 50 cc, with a compression ratio of around 10:1
In the petrol engine the fuel and air are ready mixed as a homogeneous vapor at just the right ratio of fuel to air for perfect combustion. All the fuel ignites relatively completely, with the exhaust being mainly C02 and water vapor. Power is controlled by “throttling” the air intake, so reducing the volume of the fuel and air mixture but without changing the ratio of fuel to air. In the diesel, power is controlled only by reducing the amount of fuel injected, so that at low power there is much more air than will be used in combustion. Because of the high compression and the denser nature of diesel fuel, the combustion temperature is much higher. Taken together, the high temperature and excess oxygen both facilitate oxidization of nitrogen in the air in the combustion chamber, so producing the nitrogen oxides. Also, only the fuel in contact with the air will burn, and so as the fuel is sprayed in, there is a flame front with complete combustion at the fuel/air boundary and less complete combustion further back, and this is where some of the other pollution comes from.
A number of solutions have been tried. One is a short pre-injection to mix fuel and air before it starts to burn, followed by a longer injection into that mixture once it starts to ignite, so making burning more complete. Another method diverts some of the exhaust back into the air inlet to reduce oxygen and combustion temperature, and then there is the “blue” additive (a fancy name for what is mainly ammonia and urea) sprayed into the exhaust, where it has a chemical reaction with the nitrogen oxides to break them down again to nitrogen and water vapor. Filters in the exhaust system deal with the particulates.
If all this was not enough, biodiesel fuel, being plant-based, has more oxygen (and possibly nitrogen) in the fuel itself, so that nitrogen oxides are likely to be even higher. However, it is the case that careful design of diesel engines can reduce pollution to the same or less than equivalent petrol engines. In a recent report, testers found that some diesels, including BMW 5 Series, Mercedes E Class, Audi Q2, Seat Alhambra, and VW Golf models emitted less than 80mg/km of nitrogen dioxide pollution in real-world tests, making them cleaner than many petrol cars. This is where 80mg of NOx as a maximum is the Euro-6 standard for diesel engines, but these cars actually meet it in real-world driving, rather than just pretending to do so in laboratory tests. The same report stated that some other Euro-6 diesels emitted up to 10 times the maximum nitrogen dioxide in real world tests. So if restrictions and bans on diesels are to be rational, they must be based on real-world tests, and not these misleading laboratory tests used to define Euro-6 standards.
Diesel in Shipping
At sea, ships burn heavy fuel oil that contains thousands of times more sulphur than road diesel. Heavy fuel oil is pretty much the dregs of the fuel refining process, and is therefore cheap and plentiful for shipping to use.
Many of the world’s main shipping routes pass close to coastlines, subjecting inhabitants to dangerous pollution. Ships are also responsible for huge carbon emissions. If shipping was a country, it would be the 6th largest emitter of CO2 in the world, but it has no plan in place to reduce its emissions, and shipping emissions are not included in the Paris Agreement.
Shipping, without intervention, is likely to increase emissions from somewhere between 50% and 250% by 2050, which would seriously undermine any chance we have of keeping warming below 1.50 C.
There are alternative energy sources that could be used for shipping. In addition to using wind directly, there are many green alternatives to enable electric drive for ships, including combinations of batteries, solar, hydrogen fuel-cells, and hydrogen derived from stored liquids such as formic acid and from ammonia. Also, biodiesel can be used as a direct substitute for heavy fuel oil, or for a diesel-electric configuration, as used in diesel-electric railway engines, where the diesel engine runs at the optimum speed for efficiency and drives a generator to power the all-electric drive.
The old sailing clippers were as fast as many modern cargo ships, but the large crew would be too expensive and the work too dangerous for modern times. However, if the solid masts were replaced with hydraulically-operated telescopic tubes, and the sails replaced with large single sails on a roll, sail could be hoisted, furled, and angled all by one person, or even an autonomous system. That would have to be better than those unwieldy solid wing-like sails that could be dangerous in a storm. Captains would need to learn how to sail again. Unlike the old clippers, there could be electric drive for ports, and when wind is insufficient.
Whatever is used, it is likely that a diesel generator would need to be on board as a backup at least, and using biodiesel would be better than fossil fuel, especially the very polluting heavy fuel oil used currently.
Burning wood emits similar levels and a similar range of pollutants as burning coal, though smaller amounts of sulphur dioxide and mercury, and a greater quantity of volatile organic compounds such as polycyclic aromatic hydrocarbons, (PAHs) and particulates. The largest volume of pollutants are nitrogen oxides (NOx), carbon monoxide (CO), small particulates (PM10, including PM2.5), and sulphur dioxide (SO2), as well as carbon dioxide (CO2).
Burning some woods also results in a wide range of other pollutants, such as antimony, arsenic, cadmium, chromium, copper, dioxins, and furans, lead, manganese, mercury, nickel, selenium, vanadium, and zinc.
The level of pollution depends on the efficiency of combustion and the presence of any secondary combustion. Combustion with high oxygen and temperature levels will produce less CO but more NOx, and low oxygen and low temperatures will produce high levels of CO and lower NOx, Where the combustion is at a high temperature and prolonged in a secondary process, some pollutants such as particulates might be further oxidized.
An example of a device providing prolonged combustion at high temperature and oxygen levels is what is known as a “rocket stove.” In this, small quantities of material in the form of long sticks are held in a gravity feed hopper. The combustion chamber is just at the bottom of the hopper, so that it is the bottom of the sticks that are alight. The combustion chamber is at the bottom of a short chimney (imagine a letter “J”, where the short upright is the hopper, the long upright the chimney, and the combustion chamber the base of the letter “J”), and a very strong draft is created through the hopper, and usually a secondary air vent through the combustion chamber, and up the chimney. The combustion chamber and chimney are heat insulated, so that they get very hot, so increasing the draft and combustion temperature. It is called a “rocket” stove because once it gets going, the draft is strong enough to create a roaring rocket sound. It is this strong draft that prevents any smoke or flame escaping up through the hopper. The chimney is enclosed by a flat-topped steel cylinder, much like an upturned oil drum (literally an upturned oil drum in some home-made devices), with a vent to release the hot flue-gases. These stoves burn at a very high temperature, with a very high oxygen level, but use very little wood, so they are very efficient. It is claimed that the flue gases are almost entirely CO2 and water vapor, but I haven’t found any proper studies that present any precise measurements, and I see no reason why nitrogen oxides should not be formed, along with the PAHs and other pollutants from wood. It is normally the case that the hotter the combustion, the higher the incidence of NOx. So, where it might be possible to minimize pollution from wood combustion by careful design, it is not certain, and a reasonable objection remains against burning it on the grounds of that pollution.
Bioethanol is ethyl-alcohol, the same type of alcohol found in alcoholic drinks. It can be produced from any plant material containing sugars, such as sugar-cane, potato, cassava, and corn, but less obviously hemp, waste straw, willow, sawdust, reeds, and grasses. There is even research and development into the use of municipal solid wastes to produce ethanol. Also, cellulosic ethanol (from plant cellulose) has potential, because cellulose fibers are a major component in all plant cells and are available as waste material. There is an alternative process to produce bioethanol from algae, where the algae grow in sunlight and produce ethanol directly, which is removed without killing the algae. This is 15 times more productive per acre than using corn.
Ethanol is most often used as a replacement for petrol (gasoline), but it has much less energy by volume, so to replace the energy of 1 gallon of petrol it takes 1.5 gallons of ethanol. However, it is very clean burning, and can be used for indoor heating without a flu to carry away the exhaust gases, which are purely CO2 and water vapor.
Ethanol-blended fuel is widely used in Brazil, the United States, and Europe. Most cars can run on blends of up to 10% ethanol, but many cars today are flexible-fuel vehicles, and are able to use up to 100% ethanol fuel. A flex-fuel engine has sensors to detect the blend of fuel being used, and adjusts the injection and ignition timing accordingly. Ethanol has an octane rating of 105, which allows a much higher compression ratio, so where an engine is built to run specifically on ethanol, the problem of lower energy content is largely overcome, as the higher compression ratio yields better performance and fuel economy. Some flex-fuel engines can vary the compression ratio too, either by turbocharging or by changing the engine geometry. Because of its high octane rating, ethanol can be used in modified diesel engines, and Scania has used these in buses in Sweden and the UK.
Pure ethanol is difficult to vaporize, so starting a car in low temperatures can be difficult, but that problem can be overcome by mixing it with a small amount of petrol. Various blends of bioethanol and petrol or biodiesel have been used.
· E5G to E26G – 5% to-26% ethanol, 95%-74% gasoline
· E85G – 85% ethanol, 15% gasoline
· E15D – 5% ethanol, 85% diesel
· E95D – 95% ethanol, 5% water, with ignition improver
There are engines that will run on 100% ethanol, so blending like that is not essential.
It seems that some of the objections to biofuels are largely spurious. I say this because many of these objections are based on the idea of replacing all fossil-fuels with biofuels, whereas the idea is to replace most fossil-fuel use with renewable energy and electrically powered systems. Biofuels would be used as a transitional arrangement and to continue to provide fuels for situations where a fuel burning system is the only practical solution. For example, an objection has been that to produce bioethanol from corn, there would not be sufficient land to provide for more than about 10% of petrol used today, and corn is a food crop, so should not be used for biofuel production in any case. However, bioethanol can be produced from non-food sources as we pointed out, from algae or what would be waste, and using marginal land that would be of little use for food-crop production. Even then, we would be aiming to replace ICE vehicles with EVs, and not to run them all on biofuels.
In any event, we need to change our dietary habits for both sustainability and human health. Land that is currently used for bovine rearing could be given over to feedstock for bioethanol and biogas, in addition to food crops. We also consume far too much sugar, so continuing to use the same land for sugar production, that sugar can be converted to biofuels rather than contributing to our obesity, tooth decay, and ill-health. In the same way, we consume far too much vegetable oil, so we would be doing ourselves and the world a favor by converting it to biodiesel.
Wood-burning, I think, is something we should not be doing, as burning wood produces pollution, and for the present, we need to be planting trees, not cutting them down for firewood, because we need all the forest we can get to absorb excess carbon dioxide from the atmosphere. All our forests need to be preserved, and certainly not burned down as in Indonesia to provide land for palm-oil plantations.
Biodiesel in itself is not harmful, provided that the land used for its production is well managed and essential food production is not diminished. The burning of biodiesel can produce undesirable pollution, but as we mentioned in the section on biodiesel, it is possible to make diesel engines which are relatively clean. It would be especially advantageous to use biodiesel for shipping, in combination with sail and electrical drive systems, in place of the highly polluting heavy fuel-oil currently in use. Also diesel engines can be run on 95% ethanol. It would be best to move directly to electrical drive systems for all vehicles that currently use internal combustion engines.
Bioethanol, biogas, and hydrogen are the least polluting fuels. Bioethanol and biogas can both be produced from waste and from non-food crops using marginal land. Where using waste, the CO2 and Methane would be released into the atmosphere if not converted to biofuel, which would be much better waste management. The creation of an industry for the production of bioethanol and biogas would provide farmers with many more opportunities for diversification and to make money from land which is currently unproductive. It would be a great boost to the rural economy, providing much needed income and jobs without any detrimental effects to food production or land management. As it might take some time to convert to all-electric households, the complete replacement of fossil-fuel gas with biogas would be a very desirable transitional and ongoing measure.
Currently in the United Kingdom, the government is missing a huge opportunity to exploit and develop our potential to be self-sufficient in gas, using biogas. The government is intent on replacing coal-fired power stations with gas-fired power stations, which are less polluting but which produce only marginally less CO2. To achieve this, it has a blinkered vision of fracked gas wells across the country, destroying our countryside, and exposing the water table to contamination risks. With more foresight, awareness, and wisdom, it could be solving the gas supply problem, enriching our rural communities, and increasing biodiversity all at the same time by planning, coordinating, and developing a biogas industry. The same might be true of other countries.
There is great potential for the development of biofuel industries, and governments need to be playing a role of central planning, communication, and regulation to ensure this is achieved efficiently and responsibly, to provide the best outcome for the ecology of our planet and the economies of our nations.
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