Making pyrolysis economic

Pyrolysis, the anaerobic heating of hydrocarbons such as wood, old tires, used engine oil, plastics, tallow and so forth, needs to be economic for it to be undertaken. Below are some suggested ways to increase the financial feasibility of pyrolysis.

 

 Energy conservation

Pyrolysis needs heat energy to cause the various long chain materials to break ('crack', in petrol-chemistry terms)  and the applied heat must be at a temperature of about 500⁰C. But, of course you don't want to be heating the great outdoors.  That is a waste of energy/money.  Super insulation is needed so that you only use  the amount of energy needed to break the bonds. An insulation material that comes to mind is the Aerogel that was used to protect the shuttles during re-entry but cost and availability might be a barrier.

Source of energy

Clearly the energy to heat the retort must be renewable.  Energy must come from hydro, wind, geothermal or solar sources.  Renewable energy continues to go down in price as the hardware to produce it becomes less expensive. There are a couple of possibilities.  With the spot-price-silliness that we have in New Zealand, electric energy is very cheap when it is in excess.  Either the pyrolysis unit can operate, only when energy is cheap or cheap energy can be bought and stored in a mega battery to ensure the continual operation of the pyrolysis unit.  

 

It may be worthwhile for the pyrolysis unit to own it's own renewable energy kit and thus be always paying the wholesale price.  This 'kit' continues to decrease in price.  With a battery as well, excess energy can be sent to the grid when spot prices are high. 

Energy is likely to be one of the largest running costs in a pyrolysis factory.  

 

Externalities

Many  waste streams  can be pyrolyzed to produce either liquid fuels or easily compressed and liquefied fuels.  Many waste streams are problematic if not disposed of somehow.   

There is now a cost to send waste to land fill and a land fill trashes beautiful pristine wild areas which are then no longer an asset to the community.  

Some wastes are direct health hazards such as the leaching of material from them into the ground water or as breeding grounds for mosquitoes (tires).  As the world warms, tropical mosquitoes that carry a range of very nasty diseases will be moving poleward.   

Many pyrolyzable wastes are a fire hazard and the by product of  burning some of them creates the toxic, carcinogenic, dioxane, and fine particulate material.  If they are sent overseas, the receiving country may simply dump them into the ocean.  There is no need to describe why ocean dumping is problematic.

    

The point is that the pyrolysis unit has to be credited for the financial cost it mitigates when a solution is not found for that particular waste and/or for the present cost of taking care of the waste.   Government action may well be necessary to ensure this.

By products

Depending on the feed stock, there are various valuable by products of pyrolysis.

Wood

The by product of wood-pyrolysis is charcoal.  Charcoal can be bagged and sold for barbecues or can be incorporated into agricultural soils, earning carbon credits.  See Terra Preta

 

Plastic (clean or contaminated)

No by products result from the pyrolysis of plastic.  It all converts back into alkenes and alkanes.  The alkenes can be converted into the more useful alkanes by saturating the double bonds with green hydrogen.  Petro-chemical engineers have methods of either bonding low molecular weight fractions into larger molecules or, on the contrary, cracking long molecules into smaller ones to get more of the desired fraction.

Electronic equipment

The pyrolysis of electronic equipment results in a metal rich ash.  As battery recycling ramps up, this ash could likely be sent to a battery recycling facility for the separation and recovery of these metals.  This sort of ash is a far richer source of metals than any natural ore although it is a rather challenging mix.  At present, waste circuit boards are sent overseas for the recovery of their metals.  Most of the weight of a circuit board is plastic.  With pyrolysis, you don't send the plastic  saving on weight and hence expense.

Used tires

By products of the pyrolysis of tires are iron, sulfur and carbon black.  Sulfur can be converted into sulfuric acid, using the oxygen which is a by product of the Hydrogen which has been produced for saturating alkenes.  Sulfuric acid is a very valuable product used in a plethora of chemical processes.  Carbon black is used in air and liquid filters, black paint and in the production of new tires and black plastic.  The iron is sent to an iron refinery where it is combined with iron ore in the smelting process.

Used engine oil

Used engine oils are very variable.  For instance some of them have additives of materials such as molybdenum sulfide.  Presumably this, and any other similar materials would remain after the pyrolysis of used engine oil.  In addition, there may be a small concentration of metal from the engines.  But I suspect that well north of  99% of engine oil should convert into the usual pyrolysis products.  The ash could probably be combined with the ash from electronic equipment and sent to a battery recycling facility.

Tallow

Tallow should not have any by products and rendering is not necessary.  It can be directly pyrolyzed.  However, if tallow is converted into biodiesel  instead of using pyrolysis, glycerine is a by product.  One has to work out if it is worth while to build a separate facility for the chemical conversion of tallow to diesel or to simply pyrolyze this waste stream.

Side economic benefit

If this whole process is kept in the eye of the public as it proceeds, it would seem likely that the petrol company responsible would gain a greater share of an ever diminishing market for petroleum products.  Parts of the output of pyrolysis can be mixed into conventional petrol and diesel, making them 'greener' and done through already existing distribution channels.

Wind energy's no good

At least that is what I read in an anti-wind farm article in our local news paper.  The reason given was that wind energy has to be used as it is produced and can not be stored.  Fortunately this is not true. 

So let's examine this question of how to get the maximum benefit from the energy from a wind farm; of how you store wind energy. 
 

Most countries generate some of their electricity from Hydro.  Here in New Zealand we are one of a very few nations which generates more than 50%  of our power  from Hydro.  Combined with our geothermal energy we have 70% of our energy from renewable sources.  Hydro is the perfect partner for wind farms.  Every unit (kWh) of electricity which is generated by wind leaves water in the dams to be used instantly when the wind isn't blowing.  Energy already stored is left in place to be used as needed.   Now, if you are on your toes, you will immediately ask what happens if the dams are full and the wind is blowing.   You see the problem.  I'll get to that in a minute.

In addition to saving water for future use, wind displaces the use of coal. In New Zealand we have one large coal fired power station.  Every kWh generated by wind leaves approximately 300g of coal in the ground* (This is  energy which is already stored).  A single 3mw wind turbine operating at a site that has a 35% capacity factor, leaves approximately 2,700 tons per year of this  non-renewable resource in the ground to be used by future generations of Kiwis. A typical 30 turbine wind farm over a 25 year life leaves over 2 million tons of coal in the ground and reduces our (expensive under Kyoto) Carbon dioxide production by over 6 million tons**. Hopefully, because of our foresight in building wind farms,  our kids won't have to burn this valuable resource but will use it as an industrial feed stock.  Thankfully, our grandfathers showed  foresight by building hydro-electric dams which is why our generation is in pretty good shape right now.  If we tried to build these Hydroelectric dams today it would take a decade just to get through the consent process.

*I have used a very conservative figure here which is for the most modern, coal-fired power stations.  The average world wide figure is above 400g of coal per kWh.  (look at paragraph 7 in the linked article)

**12g of coal plus 32g of Oxygen yields 44g of Carbon dioxide.  Hence roughly 3 2/3 tons of Carbon dioxide is produced for every ton of coal burnt

Wind also displaces the use of natural gas.  Like coal, this is a far to valuable resource to be burnt.  In the past New Zealand has used natural gas* to produce value-added methanol.  Both coal and gas can be used as the starting point for the production of a mind boggling range of value added products including fertilizers, parmacuticals, plastics, fine chemicals and so forth.  However looking at natural gas as a source of energy rather than as an industrial feed stock, every kWh of wind energy produced leaves either coal or gas energy unused (stored).

*Note that in 2012, new technology has produced a glut of natural gas which some commentators say will continue for a few decades.  Any bets on what will happen to our energy consumption with the advent of this cheap energy. 

Further energy storing opportunities come from demand balancing of our power grid (as opposed to the present, predominantly, supply balancing system).  In New Zealand we already have a crude form of demand balancing.  Many of us heat water when 'electricity-is-available' rather than 'on-demand'.  This is done by the clock rather than when  excess power is actually available. Some of us also have heat storage devices on the same circuit.   In the future, we will have the choice of operating washing machines, turning on heat storage devices, doing our cooking and so forth with cheaper 'when-available' electricity rather than more expensive "on-demand" electricity.  The critical development is the introduction of "Smart Grids" which you have been hearing so much about.  There are two levels of such applications.  If you have set your dish washer to come on when the signal for third level electricity is sent, (use now, level 1, level 2, level 3 etc. - each one a bit cheaper than the previous one), you don't want it to go off if there is a switch to level 2.  A heat storage device such as a hot water tank or space heater is a different story.  It can switch on and off instantly and as often as needed to balance the supply.  Devices that use power which can be switched on and off at any time would likely get a lower rate than devices such as dish washers.

Smart grids, of course, explain what happens when the wind is blowing but the dams are full.  At present, we would have to let the water flow over the spillway rather than generating electricity with it.  With smart grids and smart devices, the electricity company can send a lower priority signal, triggering a bunch of devices to come on line.  More electricity is used, making a profit for the company and saving money for the user and water (energy) is not wasted.

And finally, electric cars will begin to appear on our roads this year.  Not only can they be charged, for the most part, when electricity is available and hence cheaper, but there is much talk about using them as peak shaving devices to send electricity back into the grid when demand is high.  Charging 'when-available' will reduce driving costs (and use energy when the Nor-wester is blowing).  Giving back power 'when-needed' will generate a small but much appreciated revenue for the electric car owner.  It will also eliminate the need to borrow money to build an expensive peak shaving power station.

In summary, wind energy is stored in a number of ways.

#For hydro dams it is in the form of water in the dam not used and ready to go through the generators on demand. 
#For fossil fuels it is stored in fuel not used and available far into the future (very very long term storage).
#For the home owner energy is stored in the form of a linen closet of washing or a cupboard of dishes, washed when electricity was cheapest
#For the electric car owner it is stored in a battery charged when electricity was least expensive.

We have not even touched on the use of batteries which will come into their own as the technology improves.


In none of the above have we talked about methods the industry uses such as pumped storage.  That is another story.

Saying that wind farms (or any other form of renewable energy) are not effective because electricity can not be stored shows an insularity bordering on hermitage. Saying that we must have batteries to store the energy is true as far as it goes but there are many other ways of storing energy from intermittent sources.

Post Script
Since writing this blog, a Ted Talk has come out by a professor from MIT.  He is doing work on the construction of very cheap, very large batteries to store megawatt quantities of energy in units the size of shipping containers.  Thus another element is added to smart grids to make the generation of renewable intermittent energy more flexible.