Land fill gas as energy source for the foaming of glass

logo_smallIt is obvious to use waste (recycled glass) for the foaming of glass but could we use waste heat? This is probably not possible because the waste heat must be minimum at 850°C. This type of waste heat can be easily converted in electricity with high efficiency with for example an ORC-generator and will not be available for other applications.
LandfillHowever our consumption society has everywhere landfill sites which are generating landfill gas. This gas is mainly CH4 (methane, 50%)) and CO2 (carbon dioxide, 50%). The dominant process for the generation of this gas is done by anaerobic bacteria decomposing organic waste. The gas contains also a  low percentage other gases, which may be toxic.

Landfill_gas_collection_systemCH4 and CO2 are greenhouse gases, whereby CH4 has a larger GWP than CO2. Burning the CH4 to CO2 reduces the greenhouse effect with a factor 9. As a consequence, correct landfill management needs to capture the methane and flare (burn) it to CO2. However; instead of simple burning, we could use the generated heat to produce added value.

Percent_composition_of_each_major_component_of_landfill_gas_with_timeProduction of cellular glass could be an option, where the landfill gas is used to heat the foaming furnace. Landfill gas is not stable (changing CO2/CH4 ratio) and for that reason, the glycerin process (for example GLAPOR)  with a neutral furnace atmosphere is a better option than the carbon black process with its reducing atmosphere. Indeed, in the latter case, the burner system is much more critical because it delivers the temperature AND the reducing atmosphere.

A typical cellular glass production line for 100000 m³/year needs a certain magnitude of landfill. We found a USA document about the landfill  gas production of municipal solid waste (MSW) and could read: One million tons of MSW produces roughly 432,000 cubic feet per day (cfd) of LFG and continues to produce LFG for as many as 20 to 30 years after it has been landfilled. 

Further we know that:

  • GLAPOR cellular glass needs only 1400 MJ/m³ cellular glass primary energy. For a production line of 100000m³/year, we need an energy source of 4.7 MW.
  • 1m³ landfill gas is 0.5m³ CH4 or about 17 MJ/m³ landfill gas combustion heat.
  • 1 million ton MSW produces 510 m³/h landfill gas (432,000 cubic feet per day).

This gives how much million ton MSW we need to drive that plant for about 20 years: 4.7 / (510*17/3600) = 1.95. We need about 2 million ton MSW to produce 100,000 m³/year cellular glass during 20 years.

According the same document: Approximately 251 million tons of MSW were generated in the United States in 2012, with less than 54 percent of that deposited in landfills. This means that every year enough MSW is deposited to drive 100 cellular glass production lines of 100,000 m³/year for 20 years or 100 x 2 million m³ cellular glass in total. This amount of waste is generated with 322,369,319 people. The average citizen in the USA (and probably also in the EU) generates yearly enough MSW to produce landfill gas for 0.62 m³ cellular glass.

Maybe I made an error and I wait for a focused reader to find that error. If not, I will probably dream about free of charge (if not with a few € waste deposition charge)  MSW landfill, combined with a pile of broken bottles where a production line (a few hundreds meter long) is fabricating durable cellular glass to build passive houses with a sales price of about 100 €/m³cellular glass. Waste converted in a durable product to eliminate CO2 production during house heating / cooling, what do we need more to save the planet? Indeed, waste is big money and may help to stop the global warming of our plant. Landfill without landfill gas capture and utilization is a crime.

CO2 warming


Cellular glass versus phenolic foam

logo_smallI found a paper (TECHNICAL BULLETIN 0314) publised by dyplast products with a benchmarking between cellular glass and phenolic foam. These comparisons could be a problem in Europe but are allowed in the USA. Due to the large risk for a law suit in the USA, I may assume that the given facts in the paper are correct. But it is not sure that all relevant facts are given. In that perspective, I found another paper, published by The Dow Chemical Company, Midland, MI (U.S.A.)Also in this case, I may assume that the facts are correct.

In the last paper, I found the following:

  • Claimed benefits were high insulation value and excellent fire resistance. High moisture absorption potential and residual acid present in the foam allegedly resulted in significant corrosion issues. Class action lawsuits were filed against corporations in the early 1990’s. Past litigation in North America focused on corrosion allegedly caused by phenolic foam used in metal deck roofing applications. The resultant roofing failures and subsequent litigation are still fresh in the minds of the building community.
  • 800px-Formaldehyde-2D.svgCommercial phenolic foam insulation is made from a resole resin in the presence of an acid catalyst, blowing agents and surfactants. The resole resin is synthesized via a base catalyzed reaction of phenol and formaldehyde in a 1:2 ratio where there is a twofold excess of formaldehyde in the reaction mixture.
  • Liquid chromatography (LC) was used to determine
    the amount of unreacted formaldehyde monomer
    remaining in the phenolic foam samples. The total
    residual formaldehyde found in both phenolic foam
    samples ranged from 137 – 264 ppm. (Table 7)
    As a comparison, the raw materials used to produce
    PIR and XPS foam do not measure a reportable level of
  • The phenolic samples evaluated in the modified test result in a solution with a pH less than 4.0. This could raise concern regarding potential corrosion issues when these products are used in contact with iron and steel.
  • The water absorbed by the foam samples over the 90 day test period had a detrimental impact on thermal conductivity. After 7 days of submersion, both phenolic samples had lost enough thermal resistance to perform inferior to both PIR and XPS foams. As the duration of the test continued, phenolic Foam A dropped to 50% of the original measured thermal resistance performance. Phenolic Foam B dropped to 35% of the original performance. Comparatively, the XPS maintained 97% over the same period, and the PIR sample maintained 82% of its original performance.

In a prelimnary Britisch Standard, BS_xxxx_1_7_2010 , I found in Annex A (informative):

  • b) In designing insulation systems with phenolic foams, care should be taken to prevent ingress of water.
  • c) Adequate precautions should be taken to prevent moisture being interposed between metal and foam surfaces.
  • d) For normal use, rigid phenolic foam materials are suitable for use in the temperature range – 180 °C to + 120 °C.
    NOTE The lower temperature limit is selected to indicate the unsuitability of these materials for insulation of liquid oxygen plants. These materials can however be used at temperatures down to – 200 °C provided that precautions are taken to prevent the condensation of atmospheric oxygen in or on the insulation.

This seems to confirm the above about water absorption and corrosion.

About formaldehyde, I found the following on Wikipedia.

  • There is also research that supports the theory that formaldehyde exposure contributes to reproductive problems in women. A study on Finnish women working in laboratories at least 3 days a week found a significant correlation between spontaneous abortion and formaldehyde exposure, and a study of Chinese women found abnormal menstrual cycles in 70% of the women occupationally exposed to formaldehyde compared to only 17% in the control group.[43] There have been no studies done on the effect of formaldehyde exposure on reproduction in men.
  • The formaldehyde theory of carcinogenesis was proposed in 1978.[44] In 1987 the U.S. EPA classified it as a probable human carcinogen, and after more studies the WHO International Agency for Research on Cancer (IARC) in 1995 also classified it as a probable human carcinogen. Further information and evaluation of all known data led the IARC to reclassify formaldehyde as a known human carcinogen[45] associated with nasal sinus cancer and nasopharyngeal cancer.[46] Recent studies have also shown a positive correlation between exposure to formaldehyde and the development of leukemia, particularly myeloid leukemia.[47][48]
  • Indeed, this IARC paper clearly states: Formaldehyde is carcinogenic to humans (Group 1).

hazsymd2About the IARC classification, we find in Wikipedia:

  • Group 1: carcinogenic to humans: There is enough evidence to conclude that it can cause cancer in humans.
  • Group 2A: probably carcinogenic to humans: There is strong evidence that it can cause cancer in humans, but at present it is not conclusive.
  • Group 2B: possibly carcinogenic to humans: There is some evidence that it can cause cancer in humans but at present it is far from conclusive.
  • Group 3: not classifiable as to carcinogenicity in humans: There is no evidence at present that it causes cancer in humans.
  • Group 4: probably not carcinogenic to humans: There is strong evidence that it does not cause cancer in humans. Only one substance – caprolactam – has been both assessed for carcinogenicity by the IARC and placed in this category.

We can also state the following about GLAPOR cellular glass:

  • uses during production or contain only products belonging to a IARC group 3.
  • is absolutely non-combustible like every mineral
  • is absolutely vapor tight
  • does not absorb water at all

By combining the original benchmarking with the above facts, we come to a more profound benchmarking. Can we compare phenolic foam with GLAPOR cellular glass? Can we compare a Elon Musk Tesla car with a software manipulated diesel car? That is up to the reader of this blog, we only made the extension of the original benchmark, to be used by every cellular glass sales man on earth.


The cellular glass mold process, in words and pictures

logo_smallPINOSKLO (pina = foam and sklo = glass) is a producer of cellular glass in Ukraine. On their website, they give detailed information about the production process, which is very exceptional in the cellular glass world and for which we are greatful. In the following, I will use some of their pictures to explain the process.

They use window and container waste glass without remelting like for example GLAPOR. This is clearly the ecologic approach, also advised by BELGLAS.

The glass is ground and mixed with carbon black. It is not clear whether the carbon black addition is done during or after grinding.


The powder is put in molds, which are introduced in a foaming furnace. The entrance of the foaming furnace has a door to keep a reducing atmosphere inside to avoid that the carbon black burns before sintering is performed. The website mentions 1000°C which is rather high. The molds have a separate bottom.


The foam is stripped from the molds and introduced in an annealing furnace.



The website mentions that the speed is very critical. They use a method I have never seen. Normally, blocks are annealed like bottles in a hollow ware lehr with forced convection (ZES FOAMGLASS). But this factory pile up the blocks for their travel through the annealing furnace. We observe few yellow lines on the surface of the blocks, probably due to too fast cooling between stripping and entrance of the lehr. The following pictures show the block annealing in this case and a bottle glass lehr. The advantage of this lehr is that draft is almost eliminated.


bottle glass lehr

After annealing, the blocks are finished (ground and sawed) to the requested dimensions. The waste is converted in cellular glass gravel, which is also a very ecologic approach.


A part of the production is coated with hot bitumen.


We learn that block annealing can be done with piles of blocks, which travel very slowly through the lehr, probably without the use of forced convection.

This factory is really a nice initiative in the cellular glass world. They clearly have still a margin to improve and to produce cellular glass, affordable for every individual, who is able to buy high density mineral wool. The published thermal conductivity / compressive strength is the typical value for cellular glass, foamed directly from waste glass without remelting.


Mice like thermal insulation except cellular glass

logo_smallWe found a paper about rodents in thermal insulation and the damage that may be induced. In this paper, even the cost and the payback of protection against mice are calculated. The abstract is given hereunder.

Commensal rodents have become increasingly troublesome and damaging pests in insulated structures. Modern poultry and livestock confinement buildings in the Midwest often have insulated walls and ceilings. These buildings usually provide an optimum habitat for rats and mice; the rodents gnaw, tunnel through, and nest in the insulation, decreasing its insulative value. Such structures are known to be heavily damaged within a matter of months when commensal rodents have access to wall spaces
and attics.
We have developed an economic threshold model to help livestock producers or building managers decide when to conduct house mouse (Mus musculus) control in such situations. The model is based upon the cost of house mouse damage to commonly used types of insulation in walls, as measured in laboratory experiments.
Components of the damage are 1) the cost of insulation replacement and 2) increased heating costs due to damaged insulation. Damage costs are compared to the expense of conducting mouse control using anticoagulant rodenticides in permanent bait stations located throughout the structure. The model concludes that it is cost-effective to implement a baiting program for mouse control in nearly all insulated confinement buildings. The cost of control is usually very small when compared to the cost of potential mouse damage.

It is clear that the above is also a good reason to use cellular glass. Indeed, rodents can not penetrate into the cellular glass, it is too hard. As an example,  GLAPOR cellular glass is a perfect permanent alternative to avoid any rodent damage. The in the paper described method, rodenticides is a far too risky method for children and other animals.


Is it possible to temper cellular glass? No.

logo_smallBELGLAS gives education to glass engineering companies, who want to extend their scope to cellular glass. Indeed, from float glass to endless ribbon foamed cellular glass is only a small step.

A typical question is always: “Can we temper cellular glass?”. The answer is “No” and in the following I give the “Why”.

barrBy this occasion, I want to introduce the very nice work about glass tempering by Jonathan Barr, namely “The Glass Tempering Handbook“. After a good introduction about glass, soda lime glass, the float glass method, stress in glass, he comes to the tempering of glass. It can be a good help to understand the following.

The first thing to understand is why tempering is done. The following figure shows you that the glass plate comes much more resistant against bending. After tempering, the compressive stress on the surface works against the bending tensile strain on the bottom surface. Like already explained, the weakness of glass is located on the surface,when tension is applied, but the bulk is extremely strong. The large tension stress in the bulk is for that reason not at all a problem.


Like can be find on the PRODUCTS page, also cellular glass has compressive stress on the surface and tensile stress in the bulk after annealing or fast cooling. However, cellular glass is in fact one big glass surface, also in the bulk. For that reason, it is rather weak to tension forces in the bulk, contrary with not-foamed glass. This is why tempering is not possible for cellular glass. Too fast cooling in the annealing range induces too much residual tension in the bulk, causing spontaneous breakage.



If we want a higher bending strength, we need to work with thicker cellular glass at a higher density. Tempering is never a solution for cellular glass.

Passive houses need windows

logo_smallA reader commented on our suggestion to use cellular glass for a catenary house. If we would work with a catenary tunnel, we could use 100% glass for the side walls, because the catenary tunnel is self supporting.

But in that case, we have to use the best thermally insulating glass possible. This particular reader focused my attention on double pane  low emissivity glass with one or more transparent polymer layers between the two panes. In that way, we obtain the thermal equivalent of triple or quad pane glass but with the weight of standard double pane glass. Versions filled with Krypton are even possible.

As a consequence, the window frames can be lighter than for triple pane glass and I guess that a polymer film instead of a glass pane is also a lot more ecologic. In the extreme case of quad glass with Kr filling, we obtain  U=0.4 W/(m2K), which we have to compare with the 0.15 W/m2K for the catenary wall. The extreme U=0.4 W/(m2K) can also be reached with triple glass with special coating and gas filling.

More information can be found in the following files:

In fact, the window industry made a nice evolution in W/(m2K)

  • single pane: 6.2
  • double pane: 2.7
  • double pane with low E coating : 1.66
  • triple lowE coating with Ar: 0.90
  • triple lowE coating with Kr: 0.61
  • quad (polymer film) low E coating with Ar: 0.49
  • quad (polymer film) low E coating with Kr: 0.40

The window industry improved with a factor 15 but the above values have to be compared with the 0.15 W/(m2K) for a passive housing wall in Belgium and 0.1 W/(m2K) in Sweden. In fact, windows have to be oriented and installed in such a way that also solar heating can be absorbed in winter without over heating in summer.

About the Swedish Building Product Declaration

logo_smallA customer asked to prepare the file for a building product declaration in Sweden. Therefore I had to study the assessment criteria. They have three levels: Recommended, Accepted and To be Avoided. Besides the usual questions, the following points were remarkable:

  • Besides the actual composition, a lot of questions handle about carcinogens, mutagensreproductive toxins and endocrine disruptors.
  • Special attention was given for Lead (Pb) and Arseen (As). Both elements have a past in the glass industry but are today eliminated.
  • Also a lot of other substances are mentioned, which have nothing to do with the (cellular) glass business.
  • Renewable raw materials and recovered material must be at least 50% for the highest level “recommended”.
  • The usual things like energy consumption during production, recycling after use, packing, last production place, … are of course also requested.
  • Information about internal electric and magnetic fields is also needed although unimportant for cellular glass. These questions are new in the bussiness.

For cellular glass, I guess that only the foaming agent may possibly become a difficult point for the “recommended” level, which is 0.1% for substances “possibly carcinogenic to humans”. Today, glass is (industrially) foamed with glycerine, carbon black and silicium carbide. Carbon black (as example: PINOSKLO) and silicon carbide (mineral activator for MISAPOR) have both a classification about  cancerogenicity.

  • Carbon black is possibly carcinogenic to humans (Group 2B).
  • Fibrous SiC is possibly carcinogenic to humans (Group 2B)

Today, no classification can be found for glycerin (glycerol). As a consequence, we expect that glycerin foamed glass (GLAPOR and most glass foam gravel products) will get a level “RECOMMENDED” in Sweden.

Rusnano builds ICM Glass Kaluga, a foamed glass gravel plant.

logo_smallI found a announcement  about foamed glass gravel on the Rusnanogroup website. It was already mentioned in a previous post.  I have also downloaded  the pdf-file. The plant will produce another 300 000m³ yearly.

I was a little bit surprised by the magnitude of the investment. 1.8 billion Russian rubles was about 40 million € end 2013. This is a rather high price for this equipment and unfortunately, it will feed again the image that cellular glass has to be expensive.

The product has a “gravel density” of 160 kg/m³ and thermal conductivity of 0.08 W/mK. I copied the following cell structure picture from the pdf-file. It can be observed that it is indeed a closed cell structure.


At the right of the following picture, we see the exit of the foaming furnace with the unbroken foam.


On the website of Investments Kaluga region I could find a few other pictures, showing the entrance of the foaming furnace with the loading system and the thin sheet, making the mesh belt powder tight.


Flag_of_Russia.svgAfter the STES-investment for cellular glass boards, we have a cellular glass gravel plant in Russia. But this is only the start in this country, where combustible thermal insulation is not popular.


Combustible facade thermal insulation

logo_smallA reader has sent me an article about a recent fire in Dubai.


I copy a part of the text:

According to the news site The National the exterior cladding on the hotel was Aluminium composite panels, which consists of combustible foam insulation sandwiched between Aluminium covering. This type of cladding is used on many high rise buildings in Dubai and have been implicated in previous fires such as the one in the Torch last year. Dubai changed their fire and life safety code in 2013 due to previous fires in high rise buildings; setting stricter requirements to the fire performance of external cladding material. But as described by The National most of the high rise buildings built in Dubai before that have non fire rated exterior panels. So Dubai is facing a severe fire safety challenge, which they now have to address.

The fire is also on YOU TUBE.


The amazing fact is that the government of Dubai is changing their codes for facade thermal insulation while Europe is not following. Nevertheless, mineral wool, aerogel and cellular glass are absolute non-combustible materials.

Robust GLAPOR cellular glass boards, up to 3 x 1.5m can be installed behind a metal cladding assuring a non-combustible thermal insulation solution. It looks that even fire safety and so human life is not safe for the lobbying world.

Transport of cellular glass: trucks

logo_smallIn a previous post, we mentioned that transport of cellular glass over water would be ecologic more logic. But we did not calculate the actual primary energy contribution of transport with trucks compared to the primary energy of the production of cellular glass. We use paper about German truck transport and we assume that the actual load is optimized by using a combination of heavy load and (light) cellular glass to obtain a truck with maximum load. In the best case, we have a fuel consumption of 1.27 l/(ton 100km). We assume that we work with 120 kg/m3 density cellular glass and 1l fuel = 36 MJ. We obtain 1.27 x 120 / 1000 * 36 = 5.5 MJ/(m3 100km). Like already shown in a previous post, the primary energy of GLAPOR ware is 1400 MJ/m3. This means that for a transport to the job site of 500 km, we consume 28 MJ/m3 to compare with the 1400 MJ/m3 during production or 2%. In ecologic thinking, we get the following consequences:

  • One big production line is ecologic better than 10 small production lines distributed over Europe because a big production line is always more efficient. Reduced transport can never compensate this.
  • This plant is best located close to water transport (if not at a canal) because a ship is ecologic better than 32 or even 58 trucks.