New Zealand has a mountain of spent tires, plastic, (much of it contaminated), wood wastes, tallow from abettors used engine oil, paper and cardboard, lignin from the paper industry, wood slash, electronic equipment that is largely plastic, feathers from the poultry industry and even old clothes with no recycle value. All these and probably many other waste streams can be pyrolyzed. So what is pyrolysis.
If you light some wood on fire, you see flames. What are the flames. When you heat wood, it turns into a gas and the gas ignites. You see this as flames. The heat of the flames gassifies (pyrolyzes) more wood which continues the burning cycle. Wood has a basic formula close to CH2 but the gases approach CH4 so there is carbon left over. This is the charcoal that you see in the later stages of the combustion of wood.
Pyrolysis (gasification / destructive distillation)
Any material composed mainly of Hydrogen and Carbon, if heated in a retort without oxygen, breaks down into a range of chemicals, many of them alkanes. Classically, the lighter gaseous fractions of the output is cycled back to the retort and burnt to provide the heat to power the process. That is simply a waste. The lighter fractions from pyrolysis are 'Natural Gas' and can be compressed into tanks and used for domestic heating and cooking. The lightest fraction, methane, can be turned into methanol, if this is economically worthwhile, as we have done for years In New Zealand. We have used the methane from oil wells but can equally use methane from pyrolysis.
Pyrolysis (gasification / destructive distillation)
Any material composed mainly of Hydrogen and Carbon, if heated in a retort without oxygen, breaks down into a range of chemicals, many of them alkanes. Classically, the lighter gaseous fractions of the output is cycled back to the retort and burnt to provide the heat to power the process. That is simply a waste. The lighter fractions from pyrolysis are 'Natural Gas' and can be compressed into tanks and used for domestic heating and cooking. The lightest fraction, methane, can be turned into methanol, if this is economically worthwhile, as we have done for years In New Zealand. We have used the methane from oil wells but can equally use methane from pyrolysis.
Let's be more ambitious and set up a dedicated wind turbine and/or solar panels to provide the energy for powering the pyrolysis process and utilize the lighter fractions. A bank of Zinc Bromide or liquid metal batteries or even the ever developing Li mega batteries can smooth out the power supply with any excess sent to the grid. As with any battery, both of these non-Li batteries have their weak points but these are far outweighed by their other characteristics*.
*The only disadvantage of various alternate battery chemistries is their weight. On the positive side for static applications they:
- last far longer
- don't loose capacity with time
- can be cycled between 0 to 100% with no damage
- are made from cheap, readily available materials so if they achieve market share should be much cheaper than Li batteries
- will be far easier to recycle, if you ever have to recycle them
- operate under a wider temperature range
- have a lower, or zero fire risk and hence can be shipped by air, land or sea
- need simpler charging/discharging electronics
So where would we locate the wind turbine(s)??? Anywhere with access to the grid and, of course solar panels on every roof available. We have national grids; to transfer power from where it is generated to where it is needed.
If your chemistry is a little rusty, what are alkanes
Alkanes
Alkanes are chemicals containing a chain of carbon atoms with hydrogen atoms on all the remaining bonds. Alkanes are saturated hydrocarbons meaning that there are no double bonds between the carbon atoms. In ascending order of alkane chain length are methane(CH4), Ethane (C2H6), Propane (C3H8) Butane (C4H10) and so on all the way up to very long chain tars (bitumen). [Or if you prefer, cooking gas(C1-4), gasoline(C7-9), diesel(C10-15), jet fuel(C13-16) and so forth]
Alkenes are also produced but are undesirable. With their double bonds between carbon atoms, they can link up with each other and form 'varnishes' and 'sludges' that you really do not want in your carburetor. More about turning them into alkanes later.
Tires
When tires are pyrolyzed, most of the resulting chemicals are the usual range of alkanes plus carbon and steel. The steel is from the steel reinforcing in the tires. The steel can be accumulated in rail cars and shipped to an iron smelter. All Steel mills use a proportion of recycled steel along with the newly mined Iron ore in their retorts. Carbon is used in the manufacture of products such as black plastic pipes, black paint, filters and new tires.
If the pyrolysis unit is located within the grounds of an oil refinery the mixture of alkanes, from all varieties of feed stock, can be fed into the fractionation towers to separate out the various components. Some rubber contains sulfur which is used for the vulcanization process so tires can be rich in sulfur. Some oil refineries are already set up to remove sulfur from 'sour' crude oils. Hydrogen is used for this process.
Sulfur is a valuable by-product and is a much use element in many industrial processes and particularly for the production of Sulfuric acid which is used in many chemical processes including the recycling of the materials in spent batteries. New S/Li batteries are now coming on line providing a further market for S.
Oil refineries use various methods to 'crack' long chain hydrocarbons to obtain a larger yields of the most needed fractions such as gasoline, diesel and aviation jet fuel and this can be similarly done for the output from a pyrolysis retort. Note that in Finland, a plant to convert tires back into petrol has been set up and is reported to be pollution free. I suspect this is because they use renewable energy to heat the retorts rather than burning part of the output.
Wood waste and paper
The usual chemicals are produced when wood or paper is pyrolyzed with char (charcoal) as a by product. Wood char is a great soil additive which has a similar function to humus in the soil. Charcoal has a very long life in the soil and hence results in a long term sequestering of carbon. At present, it is not economically worthwhile to produce char for farmers but with a pyrolysis unit producing a lot of this material as a by product, the price of charcoal might well come down. The petroleum products produced from wood are green and the charcoal sequesters carbon from the atmosphere. In this case a net sequestering of carbon results in the production of Petroleum products from wood. Wood-pyrolysis is not carbon neutral but is actually carbon negative.
But the possibilities for wood pyrolysis go beyond this. Consider this scenario.
You have a plantation of trees (NZ has many of these) that you grow specifically for the production of engineered wood for the construction of single and multi-story buildings.
(1)For a start, this sequesters a significant amount of carbon in the structure of the building. As the various parts of the forest mature, they are cut and replanted.
(2)Young trees which you replant, grow quickly, sequestering carbon at a rapid rate (sigma curve).
(3)All the waste wood is pyrolized and the amount of petrol you must extract from the ground is decreased by the amount of bio-fuel produced.
(4)The charcoal is incorporated into agricultural soils, further sequestering carbon over the long term.
(5)To put the cherry on the top, wooden construction displaces cement which in itself is a source of atmospheric Carbon dioxide. Carbon dioxide is emitted both from the material that is burnt to heat the cement retorts and from the breakdown of Limestone into quick lime and Carbon dioxide. With a pyrolysis unit powered by renewable energy, you eliminate one of these.
In 5 ways, by building with engineered wood and pyrolizing wood waste you have actually sequestered carbon.
For New Zealand and other earth quake prone countries, this would be particularly valuable since wooden multi story buildings are inherently earthquake proof and can be made even more so by proper engineering. If we had such an industry and buildings to show off, we could be shipping ready made engineered beams, struts and cladding to other earth quake countries.
Incidentally, wood can be made very fire resistant. This web site suggests painting on the fire retardant. Pressure treatment would be even more effective. In addition, large pieces of wood which are not nestled beside each other are not actually very prone to destruction by fire. They char but don't propagate flames. Again. fire resistance depends not only on impregnation but on engineering.
In 5 ways, by building with engineered wood and pyrolizing wood waste you have actually sequestered carbon.
For New Zealand and other earth quake prone countries, this would be particularly valuable since wooden multi story buildings are inherently earthquake proof and can be made even more so by proper engineering. If we had such an industry and buildings to show off, we could be shipping ready made engineered beams, struts and cladding to other earth quake countries.
Incidentally, wood can be made very fire resistant. This web site suggests painting on the fire retardant. Pressure treatment would be even more effective. In addition, large pieces of wood which are not nestled beside each other are not actually very prone to destruction by fire. They char but don't propagate flames. Again. fire resistance depends not only on impregnation but on engineering.
As an added benefit, any reduction in our carbon output reduces our financial commitment under Koyota and gives us 'story' to tell about our green credentials, something that is important for the export success of our agricultural products.
Lignin
In making paper, the cellulose is separated from the rest of the material in the tree. Most of what is left after the cellulose is removed is lignin and hemicellulose. Work is being done at present to turn this material into useful substances that can replace oil from the ground. In the mean time, (or if there is more of this waste product than can otherwise be used) it can be pyrolyzed just as with all the other feed stocks. Lignin and hemicellulose constitutes between 49 and 72% of the tree, depending on species and age.
In all this talk about pyrolysis, it is the final solution for any by-product or waste that doesn't have a more profitable second use.
Plastic
All Plastics, which are long chain carbon compounds, are easily pyrolyzed. The plastic doesn't have to be clean. Food wastes, petroleum products and other contaminants are pyrolyzed along with the plastic. This is a solution to our mountains of plastic and especially those which can't be recycled either because they are the wrong type of plastic or because it is not economic to clean them. Note that it was once deemed to be worthwhile, financially, to send these plastics to China before China refused to take any more. Now I understand we are shipping our waste plastic to Turkey. Surly, then it is worthwhile to send them to a pyrolysis unit in our own country and credit the pyrolysis unit with the savings in shipping.
Clearly, any waste material which has a more valuable second life would not be pyrolyzed.
Tallow
Just recently (Sept 2019) some numpti in an abattoir poured tons of hot liquid tallow into their drains. The fat congealed and totally disabled the municipal waste treatment (sewage) plant. How much is that going to cost in clean up in costs, fines and the ecological cost of raw sewage going straight into the environment while they are getting the pumps and pipes unclogged. How much better if they had accumulated their tallow in a rail car and sent it off to the pyrolysis unit when the car was full. Here we get into externalities (see below).
Electronic Equipment
Old computers, radios, communication equipment and so forth are largely plastic these days. But they also contain many metals. If they are pyrolyzed, the plastic is converted to the usual gaseous and liquid hydrocarbons but the ash left over contains copper, gold, lead, tin and Rare Earth Metals. This residue can be sent to a smelter to be separated (refined). It might be worthwhile to first chop up the electronic equipment and apply a magnetic and then an eddy current separation before pyrolysis. This will separate out some of the ferrous and not ferrous metals.
Old computers, radios, communication equipment and so forth are largely plastic these days. But they also contain many metals. If they are pyrolyzed, the plastic is converted to the usual gaseous and liquid hydrocarbons but the ash left over contains copper, gold, lead, tin and Rare Earth Metals. This residue can be sent to a smelter to be separated (refined). It might be worthwhile to first chop up the electronic equipment and apply a magnetic and then an eddy current separation before pyrolysis. This will separate out some of the ferrous and not ferrous metals.
Incidentally, I find it strange when I read articles stating that separating the different metals left from the pyrolysis of electronic equipment is too difficult or too expensive. For heaven sake, the Lanthanides all have similar chemistries to each other and are found together in ores. They are separated at present for their amazing properties. In nature, they not only occur together but are mixed with considerable gangue (waste rock). Many of the metals which are left from the pyrolysis of electronic equipment are Lanthanides but many are not and hence have considerably different chemistries. In other words these non lanthanides are easier to separate. It should be possible to sent the mix of lanthanides and non-lanthanides that are left over to wherever they separate the Lanthanides from ores
Treated timber
At present there is no place to get rid of treated (tanelized) timber. Tantalized timber contains copper, arsenic and chromium. If it is burnt and the ash applied to the soil in the mis-belief that you are adding valuable wood ash to your soil, you will have caused serious contamination. None of these metals are ones you want in your vegi garden. All the scrap, treated wood from construction could be pyrolyzed as well but one would have to make sure that these chemicals, especially arsenic, were recovered from the output of the process. At the end of a batch-pyrolysis, oxygen should probably be introduced to get rid of any remaining carbon, turning the residue into ash which is now further concentrated and can be sent to a refinery. In the future, if we demolish houses that have been built with tanelized timber, we will have no ecologically friendly way of disposing of this wood. We also have no way of disposing of offcuts of tanelized wood except to put them in a Pyrolysis would solve this problem. Over time we are contaminating our land with arsenic. And land fill should not be an option.
At present there is no place to get rid of treated (tanelized) timber. Tantalized timber contains copper, arsenic and chromium. If it is burnt and the ash applied to the soil in the mis-belief that you are adding valuable wood ash to your soil, you will have caused serious contamination. None of these metals are ones you want in your vegi garden. All the scrap, treated wood from construction could be pyrolyzed as well but one would have to make sure that these chemicals, especially arsenic, were recovered from the output of the process. At the end of a batch-pyrolysis, oxygen should probably be introduced to get rid of any remaining carbon, turning the residue into ash which is now further concentrated and can be sent to a refinery. In the future, if we demolish houses that have been built with tanelized timber, we will have no ecologically friendly way of disposing of this wood. We also have no way of disposing of offcuts of tanelized wood except to put them in a Pyrolysis would solve this problem. Over time we are contaminating our land with arsenic. And land fill should not be an option.
Nappies
A mountain of nappies, both from infants and now, more and more from the aged, are created every year. They can also be pyrolyzed. Since they will have a high water content, it would probably be necessary to bring the pyrolysis retort up to, say 1100C and hold it there until water vapor ceased to be expelled from the retort. Some other feed materials, such as wood, might benefit from a similar pre-treatment. An added benefit of an initial phase of heating a moist material to just above 100degrees C is that you expel all the air from the retort before starting the pyrolysis cycle. Remember, all this is done using renewable energy from our dedicated wind turbine or solar panels, from the excess energy stored in our batteries and from the production of sulfuric acid (the heat from burning the sulfur).
A mountain of nappies, both from infants and now, more and more from the aged, are created every year. They can also be pyrolyzed. Since they will have a high water content, it would probably be necessary to bring the pyrolysis retort up to, say 1100C and hold it there until water vapor ceased to be expelled from the retort. Some other feed materials, such as wood, might benefit from a similar pre-treatment. An added benefit of an initial phase of heating a moist material to just above 100degrees C is that you expel all the air from the retort before starting the pyrolysis cycle. Remember, all this is done using renewable energy from our dedicated wind turbine or solar panels, from the excess energy stored in our batteries and from the production of sulfuric acid (the heat from burning the sulfur).
Feathers
The chicken industry produces huge quantities of feathers in the abattoirs. Pyrolysis produces the expected range of hydrocarbons plus a fine powdery char.
Old waste dumps
Recently, here in New Zealand, a waste dump close to a river was breached by a flood, and the garbage flowed into the sea. Old dumps which must be removed for whatever reason could also be pyrolized. In the anaerobic environment in a dump, much of this material is unchanged. We could clean up the sins of our grandfathers.
Almost none of the materials which can be pyrolized are effected by being stored in a rail car until it is full. The rail car can then be sent to the pyrolysis unit, which, ideally is located within the grounds of a standard petro-chemical refinery. These cars can be tacked on to existing trains when they are heading in the right direction. There is no rush. Thus the cost of shipping should be 'reasonable'. But we must never ignore the cost of externalities as we so often do. The pyrolysis company should be credited with the cost to us, both long and short term, of doing nothing.
A way to take care of externalities might be to guarantee that the plant that is doing the pyrolysis will be supplied with it's feed stock fob the plant for free. Just a thought.
Recently, here in New Zealand, a waste dump close to a river was breached by a flood, and the garbage flowed into the sea. Old dumps which must be removed for whatever reason could also be pyrolized. In the anaerobic environment in a dump, much of this material is unchanged. We could clean up the sins of our grandfathers.
Almost none of the materials which can be pyrolized are effected by being stored in a rail car until it is full. The rail car can then be sent to the pyrolysis unit, which, ideally is located within the grounds of a standard petro-chemical refinery. These cars can be tacked on to existing trains when they are heading in the right direction. There is no rush. Thus the cost of shipping should be 'reasonable'. But we must never ignore the cost of externalities as we so often do. The pyrolysis company should be credited with the cost to us, both long and short term, of doing nothing.
A way to take care of externalities might be to guarantee that the plant that is doing the pyrolysis will be supplied with it's feed stock fob the plant for free. Just a thought.
So what else could we do in concert with a pyrolysis unit.
Side lines
With some of the electricity from our dedicated wind turbine and/or solar panels we could electrolyze water into Hydrogen and Oxygen and store it in large, low pressure tanks. Why would we want to do this? First the Hydrogen.
Hydrogen
When longer hydrocarbon molecules are cracked to make more of the short chain molecules,,,, everywhere a chain breaks, there is a free carbon bond that needs filling with a hydrogen atom. If it is not filled, alkenes are produced and as mentioned, these are not desirable in an engine. If Hydrogen is introduced into the retort at the correct temperature and with the correct catalyst, the hydrogen saturates these bonds converting the alkenes to alkanes. The pyrolysis process cracks molecules such as cellulose which are a long chain carbon molecule, again producing alkenes, so saturating the bonds is desirable. Bio-oil, if it contains alkenes, will thicken as these reactions take place if the bonds are not saturated with hydrogen. Hydrogen is also used in commercial oil refineries to remove S from sour crudes. It would serve the same purpose for the oil from pyrolyzing tires which are rich in sulfur.
So how about the Oxygen.
Oxygen
If tires are a feed stock, this will result in considerable amounts of sulfur being produced. If it is burnt in air it produces Sulfur dioxide. If mixed with water it produces sulphurous acid. - not very useful. However if burnt at high temperature in an oxygen rich environment, Sulfur trioxide is produced. Add this to water and you produce Sulfuric acid* which is a much used chemical in industry, not to mention in lead acid batteries.
* The process is a tad more complex than this but in essence, sulfur trioxide is being dissolved in water.
When sulfur is oxidized (burnt) heat is produced. It might be possible to capture this heat for use in the original pyrolysis processes.
So already we are are producing better fuel by saturating broken bonds with hydrogen and we have a sulfuric-acid-producing-plant on site. We have steel, carbon and charcoal as added by-products for sale.
Economics
Esternalities
When calculating the economic feasibility of pyrolysis, externalities must be included. Externalities are:
" a consequence of an industrial or commercial activity which affects other parties without this being reflected in market prices" (wikipedia dictionary)
For instance:
*the cost, economic and ecological, of having a mountain of tires leaching poison into the environment, creating a fire danger and providing water pools for disease carrying mosquitoes to breed in;
*the cost of a mountain of plastic sent to land fill (for a fee) or entering the environment and eventually the sea or being shipped overseas.
*the cost of having to build a new land fill sooner than would otherwise be necessary.
*the price to store mountains of materials that could be used;
*the price to our environment of having to drill for more hydrocarbons instead of reducing the amount we have to extract by using the ones we already have above ground.
*the price to store mountains of materials that could be used;
*the price to our environment of having to drill for more hydrocarbons instead of reducing the amount we have to extract by using the ones we already have above ground.
*the value of the hydrocarbons we can produce from renewable sources such as wood waste, thus further reducing the amount of crude that must be extracted from the ground while actually sequestering carbon from the atmosphere. Pyrolysis of wood results in a net sequestering of carbon due to the construction of quality, long lasting buildings and the production of charcoal as a by-product.
All these sorts of costs should be credited to the company that is operating the Pyrolysis plant. Our tendency to ignore externalities causes some of the worst ecological abuses in our society today. The government must come to the party. Only they can make sure that this happens.
All these sorts of costs should be credited to the company that is operating the Pyrolysis plant. Our tendency to ignore externalities causes some of the worst ecological abuses in our society today. The government must come to the party. Only they can make sure that this happens.
Other Benefits of Pyrolysis
Balance of Payments
The petrol-chemicals and other materials we could product by pyrolysis would reduces the amount we have to import from overseas, improving our balance of payments. The demand for oil is already decreasing as electric cars gain a greater share of the market. As the years go by, oil from pyrolysis would become a greater and greater proportion of the oil we use as this process continues and eventually would only be used for vintage cars and the production of new plastic. Despite great efforts, it is unlikely that there will be much of a decrease in the use of air line fuel or fuel for heavy machinery any time soon.
Waste Dumps
Pyrolizing as much of the material as possible that is currently sent to waste dumps will lengthen their life and ultimately, as we make use of other materials that at present go to waste dumps, we might even eliminate them. Eventually, even old waste dumps could be mined and eliminated.
Our Green Image
New Zealand depends, to a large extent, on her green reputation, for the marketing of her products and especially her agriculture products. Reducing our use of 'mined' petroleum fits within our story. "Story" is of prime importance in commercial enterprises.
Finally
In case you need another argument to pyrolize our own waste, here it is.
https://www.youtube.com/watch?v=QTU1F865JJo&t=322s
Note that as of July 2020, the levy for recycling, here in NZ, is being increased. This makes pyrolysis even more financially feasible.
Finally
In case you need another argument to pyrolize our own waste, here it is.
https://www.youtube.com/watch?v=QTU1F865JJo&t=322s
Note that as of July 2020, the levy for recycling, here in NZ, is being increased. This makes pyrolysis even more financially feasible.
1 comment:
Noble Plastics controls the entire process by facilitating connections between manufacturers of non-recyclable waste and pyrolysis recyclers, who guarantee that these wastes are handled appropriately.
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