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The Trash Dilemma

THE TRASH DILEMMA – SOME OPTIONS

Humankind has been generating garbage for its entire existence. And, for most of our existence, and still in Canada, we buried our waste, or just left it to rot. This was acceptable when we were few in number and the “wilderness” seemed endless. Today, with over six billion of us on this finite planet, we are in desperate need of better strategies and better compliance with those strategies if we are to avoid drowning in our own waste.

Let’s look at a promising strategy for dealing with wastes. We will consider solid municipal waste for the moment. As everyone knows, we are running out of places to dump waste. Toronto trucks its waste to Michigan, which obviously cannot continue, and several plans to use old mine pits have run into strong opposition from neighbours of those pits. It would be almost impossible to obtain regulatory approval for a new dump site in today’s climate.

Ottawa’s Plasco Energy has developed a very promising technology. The principle is that municipal waste, the kind we put out in our green bags, is incinerated using a plasma. A plasma is a jet of gas, nitrogen or air, from which most of the electrons have been stripped, leaving an extremely hot (over 25,000 deg. F.) stream. A lightning bolt is an example of a high energy plasma, and those globe-style lamps that glow pinkish with filaments that move and pulse when you place your hand near the globe is an example of a low energy plasma.

The heat and energy of the plasma is used to break down the garbage to its basic atomic components, that is, carbon, hydrogen, oxygen, iron, etc. This is done in an atmosphere low in oxygen, as we don’t want to generate carbon dioxide. These elements recombine to form carbon monoxide and hydrogen, plus some chlorine-containing compounds, water, and slag. Slag is the non-gaseous insoluble solid residue.

So what is this residue, and what can you do with it? First, we need to take a quick look at household garbage – it is mostly paper and cardboard (cellulose), plastic wrap (hydrocarbon), and food waste (protein, fibre, water, cellulose). Some metal and other components such as calcium (eggshells and bones) and silica (dirt) may be present. When this mixture is subject to the high energy and temperature of the plasma, it breaks down into the materials noted above. The gases, carbon monoxide, hydrogen, and chlorine-containing gases are cleaned and the chlorine compounds are removed. The result is called syngas, and forms the fuel for an electrical generator. The inorganic materials, such as dirt, metal, form a liquid slag, which is dumped from the reactor into water. This solidifies the slag into a sand-like material that can easily and safely be incorporated into concrete or road-building products.

This plasma process differs dramatically from the older incinerators that used to burn garbage, stink up the neighbourhood and generate carbon dioxide and numerous pollutants. The plant in Ottawa has completed a successful test run, and tests on larger quantities of garbage are pending. The gaseous effluent (the stuff going up the smokestack) has been analysed for all major pollutants at well below Provincial standards. The costs are competitive with landfill, currently about $40 per tonne, when the revenue from the electricity is factored in. This process generates electricity at about 1.4 megawatts per tonne of waste. At 200 tonnes per day, the design capacity, this could supply about 4000 homes.

Some other issues related to this are that household garbage makes up about 35% of the total garbage requiring disposal. Even the most dedicated reduce-reuse-recycle program, where we all could do better, must have a parallel effort, with appropriate incentives, in the commercial, industrial and construction areas. These efforts will lower the overall amount of waste requiring disposal. The issue of PCBs and dioxins, which led to the phasing out of the old type of incinerators, is not expected to be a problem with plasma technology, due to the high temperatures involved, but detailed analyses have yet to be carried out. Explaining the process to a public that recoils at the word “incineration” is not easy, as the Swedish Ambassador in Ottawa pointed out recently. He described an operational state-of-the-art plasma system in Sweden, with its extensive experience treating a variety of wastes, and its exemplary emissions record.

The article in the Recorder and Times on Feb. 20th points out that the Ontario Government is looking at various options aimed at extracting energy from waste; the plasma technology is one approach.
Another technology to extract usable energy involves trapping the methane that buried waste gives off as it decomposes, and using it to generate electricity. An existing landfill is “capped”, or covered in such a way as to capture the methane, then the methane is cleaned and dried before it can be used or piped into the natural gas distribution network. There are numerous landfills where this technology could be applied. An abandoned cement quarry on Montreal Island was used as a landfill for many years, and the waste methane is currently being flared, or burned off, but it could be cleaned and piped to Montreal-area homes. As fuel prices rise, this option becomes more economically attractive.

Governments have limited practical options, but it does appear that plasma waste disposal offers several clear advantages, and deserves a realistic trial. We all contribute to the problem and we must collectively take responsibility for the solution.

A New Turn Of Events

Hello Readers... my science column was carried in the Brockville Recorder and Times, but they have come under severe cost restraints and have had to eliminate frills such as science columns. This leaves me free to use this blog for my columns, although without financial reward.
I admit to not being as diligent as I could in keeping this blog up-to-date, but now that I am not constrained by either a bi-weekly schedule or a specific length limit, I may be able to be more flexible.
I welcome your comments about the content, the tone or any other part of my blog.
Thank you for reading and please let me know what you think.

Solar Energy - Solar Heating

SOLAR ENERGY 2 – SOLAR HEATING

In my last column we looked at photovoltaics, the generation of electricity using sunlight. This week we will look at solar heating, SH.

SH is something we are all familiar with… remember those black vinyl car seats on a summer day when we were kids… ouch! Let’s see what can be done with this energy.

Solar heaters are available today in several forms, and a reasonably efficient version can be made with readily available materials. If you want to heat your swimming pool, simply putting a coil of black pipe on the south-facing garage roof, connected to the recirculating line will make a difference to your pool, and you can upgrade to more efficient designs fairly easily. In many tropical and sub-tropical countries, rooftop solar heaters are commonly used to supply domestic hot water, with small electric or fuel-fired in-line heaters to make up for cloudy days or night-time use. Passive solar heating consists of laying a floor of stone or tile in a south-facing room and allowing the low winter sun to warm it. Because stone and tile absorb heat slowly and release it slowly, this design can make a small difference to heating a room, even in Canadian winters.

More sophisticated systems can be fitted to homes to supply the bulk of the heating needs, even in Canada. These consist of a non-freezing fluid that is pumped through a flat panel collector on your roof and then through tubing incorporated into the floor, for example. The angle of the panel is critical to obtain efficient use of the sunlight, which is why you may see these mounted at awkward-looking angles. These systems require back-up power, but clearly would reduce the need for conventionally-generated power.

The large-scale generation of electricity through SH is also well advanced. In Spain a system has been in operation for several years. It involves a roughly circular field of flat mirrors, which move to track the sun and reflect the sunlight to a central tower. Inside the tower is a receiver in which a fluid (water) is heated to over 500 deg. C. and the resultant steam turns a turbine to generate 11 MW of electricity. This is over double the output of the photovoltaic plant in Arizona we looked at in the last column. As with photovoltaics, there are no emissions associated with this, but also it takes some land area, and more maintenance is required. Not everyone wants a 300 ft. tower in their neighbourhood.

The latest designs involve parabolic reflector technology. A parabola is a curve, a bit like the narrow end of an egg, which has the very useful property of focussing all the incident light onto one spot. So a parabolic reflector, in the form of a trough with a pipe containing water or glycol solution (similar to the fluid in your car radiator) running along inside it is a very effective way to capture solar heat. The catch (there is always a catch) is that the reflector has to track to sun to maximise efficiency. The good part is that you don’t need a tower, but you pipe the heated fluid directly to a generator building. Again, there are no emissions but maintenance is required for pumps, generators, and tracking mechanisms, as well as ensuring that the mirrors are kept clean. As with PV systems, there is a need for some form of storage so that energy can be generated at night and in cloudy weather. With SH systems, the latest technology involves heating a salt solution and storing it in a tank. The stored heat can be used to generate steam to run turbines and generators at night.

The world has about 500 MW of installed capacity, about 100 MW of planned capacity and about 2700 MW of announced intent to build capacity. This is a small but significant portion of our needs. All of this is in tropical or sub-tropical locations, and the newest plants use the parabolic trough technology, with computer-controlled tracking to obtain the highest efficiency. Efficiencies of about 40% have been claimed, compared with 15% for PV systems, based on the conversion of sunlight to electricity.

Currently the largest operational system is in California’s Mojave desert, with 354 MW capacity. This could supply over 300,000 homes. Even at this scale, the cost of SEGS electricity (solar energy generating system) is three to five times the cost of conventionally generated electricity. However, as we are painfully aware, the cost of fuel (natural gas and oil) is certainly not going down, so the gap is likely to narrow quickly.

So you can see that both photovoltaics and solar heating can play a significant part in meeting our energy needs, even with their known drawbacks. Their key advantage, that of generating power without accompanying greenhouse gas emissions, can only help in ensuring their widening adoption in the coming years. As well, if governments, utilities, and regulators are serious about reducing greenhouse gas emissions, they will have to encourage this kind of development through tax incentives, price supports and other inducements. Only through these actions will we see a meaningful advance in solar technologies of all types.

Solar Energy Part 1

Solar Energy – Today and Tomorrow (I)


Solar Energy…. It has a nice ring to it, doesn’t it? The answer to humanity’s need for energy, limitless, perfectly clean, harness the awesome power of the sun… all sounds grand. As with most subjects, it is both right and off base.

Solar energy can be broken into two components, and we will look at each separately. Generating electricity from solar energy is called photovoltaics, or PV. Using the sun’s heat to generate useful energy we will call solar heating, SH.

Let’s look at PV, or photovoltaics first. Scientists are able to measure the solar energy which strikes the surface of the earth quite accurately. At our current rate of consumption, the solar energy falling on one half of Manitoba is enough to meet all of the worlds’ energy needs. So research is focussed on how to increase the output of PV cells, how and where to locate them, and how to store and distribute energy when the sun is not shining.

Many of you have, or have seen PV devices. You may know them as “solar powered”… the essential component is a small window, usually grey or blue, that converts light into electricity. Some calculators and watches have a PV cell to run them, and your local auto supply store sells panels which will recharge your car battery or run a small electronic device. Solar powered radios and patio lights are also popular. All those devices work because as a photon, a unit of light, strikes the treated silicon layer inside the cell, it knocks loose an electron. When you have enough loose electrons you soon have a usable electric current. The big problem with these devices is their efficiency, or rather lack of it. A PV cell, on a good day, converts only about 15% of the sunlight that strikes it into electricity. When you include clouds and atmospheric dust, you don’t get a lot of electricity out of your cell. On the good side, huge strides have been made in recent years to advance this and experimental efficiencies of over 40% have been demonstrated. This compares with nature’s efficiency of over 95% when converting sunlight to chemical energy using photosynthesis by plants

Scientists figure that in places where there is a lot of sun and electricity is expensive, such as Italy, California and parts of Japan, PV can compete with traditional generation methods within a decade. There is a working PV system near Springerville, Arizona, that covers an area of about 50 acres. It is built so that standard modules of about one acre in size can be added as needed, and it generates 4.6 megawatts, enough to power about 3900 homes, perhaps one third of Brockville. The best part is that it does this with no emissions whatever. Even with the low efficiency of PV, maintenance and wear and tear is minimal. In our part of Canada however, with relatively cheap electricity (about 6cents/kwh) and less sunshine, PV remains marginal, powering channel markers on the Seaway, for example.

The German government is encouraging PV development by allowing producers to sell PV power to the grid for up to three times the cost of electricity generated by conventional means. This is creating a boom in technological innovations in PV. A really cool development involves a PV cell that is created by a special version of an ink-jet printer, and is laid down on a flexible sheet only a millimetre thick.

The next issue with PV is that our need for electricity and the times the sun shines do not always match, so you have to have some kind of storage and backup system. Weight and space requirements for these can be considerable. Batteries to power your house for 24 hrs. or more would be as big as your kitchen stove. Current research is tending towards compressed air in which the PV system powers compressors when the sun is shining, and the compressed air drives a turbine when it is dark. Underground caverns previously used for natural gas storage are being considered to store the compressed air.

So, to get our moneys worth out of PV, and scale it up to make it economical, we can do either of two things… set up in a desert location, preferably near the equator, and take advantage of clearer skies and a more consistent solar angle, or hoist the whole thing into space.

As to putting the whole thing into space, there are obvious technical challenges associated with getting that much hardware up there, and assembling it, but it is technically possible. Increases in efficiency of factors of three to five are thought possible because of the lack of an interfering atmosphere and the ability of the panels to face the sun continuously. The power would be beamed back to receivers on Earth in the form of microwaves. If this project were to be started tomorrow we wouldn’t be seeing any “space-generated” electricity for at least twenty years, and then at a considerable cost, but largely pollution-free. Dozens of necessary shuttle launches may make this option less attractive. This or comparable plans are unlikely to be implemented until fossil fuels are in critical short supply.

PV is on the verge of huge growth, and we can expect to see a lot more of it in all areas of the globe over the next few years. Next week we will look at solar thermal power.

Gluten

Gluten – Essential for Bread, possible Allergen

A friend mentioned to me that her granddaughter had recently been diagnosed with celiac disease, and that she was allergic to gluten. My friend asked me about gluten, and how she could spot it in foods and what to avoid. I have no wish to step into the territory of my medical colleagues, but there is quite a bit of science and chemistry associated with gluten which we can explore.

First, let’s look at the basic grains that have formed the staple food of most of humankind for thousands of years. These are wheat, rye, oats, barley, sorghum, maize (corn) and rice. Quinoa is a new (to North Americans) grain that is gluten-free. Only the first two of these yield a flour that gives bread the taste and texture we have come to want and expect. All of these seed grains consist of three parts: the embryo, which is the seed of the new plant, the endosperm, which is the store of nutrient for the developing plant, and the protective coating of the seed which ends up as the bran. In most seed grains the endosperm makes up about 80% of the bulk of the seed. This is what we make into flour, and flour consists of protein and starch. About 85% of the proteins in wheat, barley, and rye flour are responsible for dough formation, and are collectively known as gluten.

Flours from different types of wheat have different protein levels and dough-making characteristics. North American spring wheat, Canadian style, is described as “hard” by the millers as the endosperm is brittle and grinds easily. This makes an excellent bread flour. “Soft” wheat, usually made from winter wheat and more common in Europe, makes a better cake and pastry flour, where a more crumbly texture is desired. All-purpose flour isn’t, as any good baker can tell you. Interestingly, the bread-making properties of flour are improved by storage, and year-old flour will make better bread. However, most flour we buy today has been chemically aged.

So to gluten… as we noted above, glutens (there are two types) are found in the protein component of wheat, barley and rye. Because many of our foods contain flour made from these grains, people with a gluten allergy have to be very careful about their diet.

Some of the main sources of gluten in our diet are bread, pasta and cereals, biscuits, cakes pastries, some sauces and soups (which use flour as a thickening agent), vegetable oil which may be made from or contain wheat germ oil, many snack and fast foods, and beer and whisky (Rye and Scotch). American whisky is made from corn and should be acceptable. Not helpful for an eight year old, I realise.
Foods which do not contain gluten are fruit, vegetables, salads, potatoes, rice and maize (corn), nuts, red meat, chicken, fish, eggs and dairy products, and wine and cider. Potato flour or rice flour can be substituted for wheat flour, but you may not get quite the texture you have come to expect from wheat flour. Using cornstarch instead of flour to thicken sauces and gravy is an example of an easy change.
Two local nutritionists have written several recipe books with many delicious-looking recipes for gluten-free cooking. For more information, check out their website at www.bestbreadrecipes.com.

Recent research at Agriculture Canada has proven that oats are safe for celiacs. The problem is contamination from milling equipment, so look for oats milled in a gluten-free process, which are available in some health food stores.

Now we get to the effect part… the inside of the small intestine, the section right after the stomach, is lined with millions of tiny fingers called villi. These villi absorb the nutrients in the food you eat, the iron, the vitamins and minerals, the proteins etc. If you have celiac disease, your body, on exposure to gluten, produces antibodies that damage and ultimately destroy these villi. As you can imagine, this process inhibits your body’s ability to absorb nutrients. Because the symptoms are rather non-specific, you can function for quite a while, often years, without realising what is wrong. You may simply feel tired, have bowel problems, be anaemic, and have a bloated stomach. A simple test might be to remove gluten from your diet and if your condition improves over a few weeks or more, you may have an allergy. On the good side, the damage to your intestines often is reversible when gluten is removed from the diet. Without going into a long medical description, suffice it to say that if there is a gluten allergy in your family your likelihood of having the allergy is increased considerably, and if you think you may be allergic you should consult your doctor for guidance in your specific case.

It is estimated that about 1 in 300 North American and Europeans suffer from celiac disease at some level.

More and more packaging information indicates the presence of gluten, although declaring gluten on the label is not mandatory. The Beer Store now carries a gluten-free beer, and some beers are made from rice. Restaurant meals can be a bit of a problem, and it is advised to develop a relationship with your chef so that you can specify a non-gluten containing alternative. Most will try to accommodate you. Being careful and avoiding certain foods can allow someone with celiac disease to lead a normal healthy life.