Circular economy: use of wind turbines blades as combustible and mix material for cement production

One of the future challenges of wind energy is to find a solution to recycle old blades from decommissioned wind turbines. In this post I will try to summarize several possible alternatives and to describe in detail what I think is currently the best option: to use them as a component for the production of cement.

The development of this interesting technical solution started in 2005 when one of the largest wind turbine manufacturer asked LafargeHolcim (a global cement producer) to use the decommissioned blades in cement production plants.

In 2008 Geocycle (the business unit of LafargeHolcim specialized in use of waste to produce cement) launched the full scale development of the solution in the Lägerdorf cement plant, in Northern Germany.

The recycling start in the wind farm, where the blades are cut in 10 meters long pieces using a mobile cutting technique that reduce the generation of fine dust humidifying the area. The resulting water is collected and brought to the recycling plant together with the other materials.

The pieces are then transported by train or truck to a pre-processing plant.

Here the blades are cut before in segments with a length around 1 meter and subsequently shredded in smaller pieces, with a final length of some millimetres.

Metals, both ferrous and not ferrous, are separated automatically from the material flow by magnet and eddy current magnet devices.

Finally, the crushed blade dust is mixed with a humid substrate material made of other residues such as plastic labels and miscellaneous packaging materials. The purpose of this substrate is to homogenize and bind together the blade dust. The material composing the substrate are wastes from other processes such as paper recycling.

All process steps in the pre-treatment plant are fully automated and performed in a controlled atmosphere. This guarantee maximum levels of occupational health and safety.

The end product is put in the cement plant.

In the pre-calciner (an element of the cement plant that optimize fuel consumption) the resin matrix is used as an alternative fuel, substituting coal, petroleum coke, heavy fuel oil or natural gas.

At a temperature around 900 °C the resin burn transforming the blade fibers into ashes. These ashes are then going together with the rest of the calcinated raw materials - usually a mixture of limestone and clay - in the sintering zone of the cement kiln to produce the clinker.

Finally the clinker is ground into a fine powder together with a small amount of gypsum creating the final product, cement.

The cement produced using wind turbine blades is indistinguishable in terms of quality from the standard product obtained without using the blades. It can be sold in the market or used again in wind farms, for instance in wind turbines foundations, closing the loop.

This solution provide alternative raw materials for cement production, reducing the need for quarrying, stone crushing and transportation. The ash of a wind turbine blade consists mainly of silica (SiO2) and calcium oxide (CaO) and due to this substantial amounts of natural resources like carbonate rock (limestone) and clay (usually in the form of sand) can be saved.

Additionally, it has to be noted that this solution contribute to savings of fossil fuel: the resin of the blade provide energy (around 12 MJ/Kg). This value is approximately the half of hard coal:  therefore each tonne of rotor blade substitute around half a tonne of hard coal.

It’s important to note that this solution has been indicated in 2011 as the best option available in a Position Paper subscribed by the European Composites Industry Association and other relevant category associations.

The test phase was successfully concluded in 2009 and the solution has been made commercially available since 2010.

I see several interesting benefits associated with this technique:

  1. It is capable of dealing with large amounts of materials, since the cement plants can handle thousands of tons of material.
  2. It address as much as possible geographically local opportunities, because it’s operated by LafargeHolcim, a multinational company active worldwide with over 2000 operation sites.
  3. It is feasible right now, because it is a commercially mature solution currently used in Germany and neighbouring countries. Hundreds of blades have already been recycled.
  4. It is cost-effective, because is the second cheapest alternative after landfilling.
  5. It address the totality of the materials of the blades, because the resin matrix is used as combustible, the fibres become part of the cement and other elements (e.g. metallic components) are separated upfront in the pre-processing unit.
  6. It follow strict environmental and safety standards. This solution has been developed in Germany (one of the first country to ban the landfill of wind turbines blades) and it has been certified by third party bodies.

The final cost is function of several parameters, such as the number of blades to be recycled, the distance of the wind farm from the nearest cement plant and the need to adapt the pre-processing facility.

Therefore, final cost will depend on scale factors, logistic costs and pre-treatment costs.

There are several other alternative. I will try to summarize them in the next paragraphs.

Landfill: Blades are sectioned into pieces of suitable dimensions and placed in a landfill. Transportation and preliminary shredding is needed.

Here no material recovery is possible and some national and local legislation impose high landfill taxes or complete bans on composites material with high organic percentage such as the blades.

Additionally, legislation worldwide is expected to become stricter acting as a driver for the development of alternative solutions and the creation of a recycling market, either with an extended ban or with a sharp price increase for landfill of blades.

Mechanical processes: Blades are reduced in size and separate into powder and fibrous fractions via cutting, crushing, shredding, grinding, or milling processes.

Finer pieces are sorted and used as fillers or reinforcements or as fuel for thermal waste processes.

This is currently done on a limited commercial scale and theoretically it has a wide range of potential applications for material recovery.

However, from an economical point of view it is competing with the lower market cost of alternative virgin fillers (calcium carbonate, silica).

Additionally, it has been observed a reduction of the mechanical properties of the resulting material (lower stiffness and strength). For instance, concrete made using shredded blades instead of crushed stones has unsatisfactory mechanical properties.

The only viable mechanical process currently operating in the market, presented as the competitor solution, is the one offered by Global Fiberglass Solutions, detailed in the following paragraph.

Mechanical processes - Global Fiberglass Solutions (GFS) pellets: The blades are transformed into small pellets that are sold under the brand name of “EcoPoly Pellets”. They are usable in injection mold and extrusion manufacturing processes and they are made from a customized blend of wind turbine blade materials.

EcoPoly Pellets are made to order for final customers based on the requirements of the customer’s own manufacturing process. GFS has initiated distribution options for pellet and has already found several wind farmers owner willing to provide decommissioned blades as input material for pellet production.

I believe that this technique it is currently available only in the USA.

Thermal processes - incineration: Blade sections are incinerated at high temperatures – usually over 800 °C.

Organic substances are combusted and converted into non-combustible material (ash), flue gas and energy. This process is usually combined with energy production and heat recovery.

The ash could also be used as a substitute for aggregate in other applications recovering the material or landfilled. However, no economically viable uses have been found for the ashes (beside the proposed use as input for cement production).

The advantage is that there are already numerous incineration plants available and that it can be done at attractive prices.

The disadvantage is that no large parts can be incinerated, making necessary a preliminary shredding.

Additionally, blades have a high ash content (around 50% to 65%) that needs to be landfilled afterwards with the associated transport and landfill tax costs.

Finally, burning blades create residues that can cause problems in the gas filtering systems.

For all these reasons this solution has been discarded.

Thermal processes – Pyrolysis: Blades are sectioned into suitable dimensions and decomposed using heating ovens in an inert atmosphere (450-700 °C).

Material is recovered in the form of fibres which can be reused in other industries. For instance, in pilot tests they have been used for glues, paints and concrete. Other products of this process include syngas (that can later be combusted for electricity and heat recovery) and char (recycled as fertilizer)

Under certain boundary conditions the resin matrix can be transformed in an oil “Pyrolysis Oil”.

The problem with this technique is that significant amount of energy are needed to activate the pyrolysis, impacting the overall environmental value of the solution.

Furthermore, available laboratory tests show a degradation of the properties of the glass fibers and no secondary market has been found.

Additionally, test have been performed only at laboratory scale so it is considered a solution with a low technological maturity.

Thermochemical processes – Solvolysis: Chemical solvents (water, alcohol, acid) are used to break the resin matrix bonds at elevated temperatures (300-650 °C) and pressures conditions.

Among all the solvents currently tested, water appears as the most commonly used. In this case the process is called hydrolysis.

Fibre materials recovered have a similar strength and could be reused in other applications. The resins as well can be separated and combusted for energy recovery

As far as I am aware test have been performed only at laboratory scale, mainly with focus on carbon fibres composites.

Moreover, due to the low market price of glass fiber, no secondary market is existing.

Wind farm project management: PRICE2 vs PMP

In another post I have discussed my experience with the PMP certification and its (somehow weak) relationship with wind farm project management.

In a nutshell, several processes and concepts are not directly applicable given the peculiarity of our industry. Said that, I believe that the PMP has a value, because it explain in detail a lot of tools and ideas that are used daily – for instance dependency types in Gantt charts, how to handle risk management or the “stakeholder management” concept.

Some days ago I have made another PM certification, the British de facto standard PRINCE2. The main reason for that has been my curiosity to see another point of view on a very broad topic such as project management.

Both certifications are trying to live together and differentiate themselves:

  • PMP define itself as a “standard” and comes with a mountain of processes and techniques.
  • PRINCE2 define itself as a “methodology”, coming with models and templates but very few techniques.

My personal impression is that the role of the Project Manager in PRICE2 is less relevant compared to the PMP idea of the same role – basically he has some decision margins, but he’s somehow squeezed between the Project Board making the big decisions and the teams doing the actual job. As soon as one of the tolerance levels is exceeded, he need to escalate the problem to the Project Board (that in the wind industry, if it exist, is usually called “Steering Committee” or something similar).

This image is strikingly different from the one that my mentor Luis Miguel gave me when he told me that, in the infancy of the wind industry, the PM was basically “the God of construction site”. Possibly the image is a bit strong but it makes the concept crystal clear.

Said that I also had the feeling that PRINCE2 was much easier to follow in the definition of the workflow, with less processes (seven) clearly linked between them and few key concepts (“Themes” and “Principles”). Understanding the relationship between the 49 processes of PMP is not that easy: I had to print them in a huge A0 and spend a lot of time staring at it to make a sense of them.

An interesting argument that I want to mention against PRINCE2 is that it is “unfalsifiable”, in the scientific sense defined by Karl Popper. This basically means that PRINCE2 has to be tailored (that is, adapted) to the specific project to work properly. If something goes wrong, you cannot proof that the problem is PRINCE2 (because possibly the tailoring you have made was wrong).

In conclusion I would recommend both certification to people interested in knowing more about project management, even if some tools, techniques and processes are not used in wind farms construction.

PMP methodology & wind farm project management

This week I had the pleasure to pass the PMP (Project Management Professional) exam – one of the two leading certifications for project managers, the other being PRINCE2 from the UK. The exam itself is notoriously not trivial: long (200 questions in 4 hours) and based on a book very hard to read, the Project Management Body of Knowledge (“PMBoK”).

In general I would recommend it, as it provide a solid methodology together with a broad suit of concepts, tools and techniques. On top of that, a great number of terms are defined in detail and this alone is a great benefit as this facilitate the interaction with other professionals providing a common language.

Said that, and totally aware of the fact that this type of methodologies are conceived to be “not industry specific”, I believe that there are many relevant difference between the PMP concept and the way wind farm project management is today, at least seen through the eyes of Project Managers (PM) working for wind turbine manufacturers or Main Contractors.

To give some example, one of the first steps in the PMP standard is the creation of a business case for the project.  This is something that you will hardly see in wind farm construction – maybe the wind farm developer has a business case, but the company building the wind farm is selling a product (the wind turbine) and some services (BoP, installation, maintenance). No need for business justifications, this is the core business.

Additionally, in the PMP methodology the PM should start to define the scope, the deliverables, the cost baseline, etc. I believe that in general the wind industry the PM receive all this inputs from the Sales Manager and/or Tender Manager, and even if there are always open points and deliverables that need to be defined more in detail this is not the main focus of the PM.

I have also rarely seen in wind farm construction a change management system as developed as the one in the PMP standard. I do however recognize that it has a lot of sense, providing a uniformity and a logic in the way changes are analysed and approved or rejected.

Finally yet importantly, the current version of PMP (sixth edition) include a variety of Agile Development concepts. These are more relevant in software development and similar environments: onshore wind farm construction is a business where these evolutionary development and adaptive planning techniques do not usually find opportunities to be used.

Wind farm construction steps: generic timeline infographic

One of the pleasures of fatherhood is the fact that you have quite a lot of extra times during the night – if your kids do not sleep.

Yesterday night has been exceptionally short due to a son diving out of the bed and hitting his head and another who decided that at 6 AM the night was ended.

Therefore I’ve used this extra time to create a timeline with a very generic overview of a small wind farm construction steps.

They can (and do) vary a lot between a project and another. However it should give you a rough order of magnitude of the key steps and the time needed for each of them.

The editable PPT file is available on demand. It’s based on a free template made available by Hubspot (thank you guys!).


With a fair wind – something interesting to read this summer (if you like wind farms)

If you are reading this blog,  chances are that you are somehow interested in wind energy.

And if you are looking for a good, interesting book on this topic I would suggest you to start from here: With a fair wind (full disclosure – I’ve written the chapter on Civil Works).

It is a book edited by the Esteyco Foundation, who was established more than 25 years ago with the aim of contributing to the progress of engineering and architecture.

There are quite a lot of contributors including Manfred Petersen, a very experienced wind farm foundations designer who is working at several interesting new technical concepts. They are coordinated by Ramón López, who in addition to his career as an Engineer is also very active as Triathlete.

Download it here

Where do I go from here? Careers path in the renewable industry.

This post is about my personal experience with possible careers path in the onshore wind industry - what are the easy and the not so easy movements. I believe that the main concepts would be applicable to similar industries, such as Solar or Offshore.

It’s applicable to medium and big size companies organized in a classic way (Engineering design the product - in my case a wind turbine, Sales & Tender Management sell it, Project Management build it).

I focused on the departments that are near to my professional experience – therefore I’m not keeping into consideration Service and all auxiliary departments (e.g. HHRR).

The most “natural” career path is upward: you start for instance as a (Junior) Project Manager, you become a Project Manager, Senior Project manager, maybe a Project Director (if this position exist in your company) and finally you land in a Head of Project management position.

What makes fun (and broaden your view of the company) is to have also “lateral” movements.

I believe that some are easier than other. For instance I know many Project Managers that become Tender Manager and vice versa, or engineers becoming Tender Manager. Somehow more rare is to see a Sales Manager becoming a Project Manager, or a Tender Manager becoming a Sales Manager.

It’s not impossible, I know a bunch of cases. However, Sales guy are usually a different class.

For instance I’ve never met an Engineer with a Sales background: I’m not saying that it’s impossible, but for sure is a less frequent (and more complicate) career move.

I tried to summarize visually the idea in the picture.

I also beleive that  moving “lateral and up” would make the change even more complicate.

For instance it would be complicate for Tender Manager to become a Senior Project Manager (or Project Director), but it would be much more complicate for a Project Manager to step into a Senior Sales Manager (or Sales Director) position.

Looking for a tender manager BoP

Looking for a Tender Manager specialized in Turnkey (EPC) wind farms.

Ideally expert in wind farm Balance of Plant (roads, foundations, MV cables, substation) and technical and commercial negotiations for all BoP scope of supply.

Apply on Linkedin or here:;sid=2ctve7ap88m7y3oy;job_pub_nr=06A416E2-A75E-454C-AB00-5062D288C634;p=homepage;job_pub_type=extern;

5 strange things that you might find in a wind farm

Working on a variety of projects worldwide I sometimes see unusual requests from customers that want to complement their new wind farm with some nonstandard feature.
I’m collecting here my personal top 5 of “...are you REALLY sure you want it?”. Even if often this type of requirements can lift considerably the price (and make the project less attractive) customers are often irremovable in their request.

#5 – Reserve main transformer. Sometime also poetically called “cold transformer” this is basically a very expensive spare parts to keep parked somewhere in the substation. With a price tag around 1 million it looks like a very expensive price to pay to have a backup in case something goes wrong with the main transformer.

#4 – Residences for the Service technician. In very big wind farm sometimes it’s a good idea to have someone on site 24/7. If the wind farm is in the middle of nowhere it can be also a good idea to provide fully furnished houses.

#3 – Gym. The same Service technician living in the middle of nowhere will presumably need something to do while they are off duty. A properly equipped gym can provide a good use for their spare time.

#2 – Mosque. With a mosque we are becoming very near to the concept of “wind farm town”. It was also a good opportunity to learn something more about the various requirements of this type of religious building.

#1 – Watchtowers. By far the most unusual requirement ever. Basically, a place where an armed guard can watch from a vantage point who is approaching the wind farm, with electricity (you will need to connect it to the substation somehow) and septic tank.

Environmental impacts of wind farms

When I talk about my job with people coming from different businesses I receive often question linked to the “environmental impact” of wind turbines.

This term include various effect related to the construction of a wind farm. They can be summarized in the following categories:

Visual impact

Are wind turbines ugly or not? This is a difficult question. Probably I’m biased, but I think they are beautiful – or at least, better than a nuclear plant, unless you like concrete cooling towers. Some nacelles shape have been designed by artist (like the first Acciona models) or architects, like Enercon’s egg shaped solution. It has been designed by Sir Norman Foster and has been awarded with the Design Council Millennium Products Award, the same prize given to beautiful stuff like the Lotus Elise.

However in several countries a specific study is done to evaluate the visual impact of the turbines. There are several indicator and methodologies, however this is usually done considering the “weighted” average height of the horizon before and after the construction of the wind farms.

Noise generation

New generation turbines use a lot of tricks to keep noise low. Noise is coming above all from the tip of the blade, being the rotating equipment in the nacelle only a secondary source. The “easy” way to limit noise is limit the tip speed of the blade. Other strategies involve special profiles for the blade and software control of the machine to limit noise emission when needed (usually during the night, and/or when the wind is blowing from specific directions).

Electromagnetic interferences

This is easy to measure. In general electricity is generated at a low voltage (around 700 Volt) and MV cables are buried, so this impact is negligible.

Shadow flickering

This is the risk that someone living near the wind farm could experience, for a prolonged length of time, the intermittent shadow of the blades passing in front of the sun. This impact is relatively easy to simulate: there are software that, given the position of the turbines and the meteorological parameters (wind direction, percentage of sunny days) calculate the amount of time an observer located somewhere near the turbine would experience the flickering.

Bird strikes

One of the most discussed issues. You will find quite a lot of studies online, done in countries were wind energy and environmental sensibility is well developed (US, Germany, Spain, etc.). In general my impression is that, compared with other causes of bird death (hunt, high buildings, traffic, etc.), impact with turbine is accountable for a very small percentage.

Additionally modern wind turbines can be equipped with a lot of technology that minimize this risk (bat detectors, LIDAR systems, artificial vision, etc.). I had the pleasure of working at projects were the space between machine was large enough to lower the risk of impact, and additionally the turbines were stopped when migrating birds approaching the wind farms were detected.


Wind farms: top 5 of myths & urban legends

A curious consequence of writing a blog about wind farms is that every now and then I’m contacted by someone hating wind energy.

In the majority of the cases, the writer also ask for help to stop or boycott a wind farm somewhere in the word, apparently ignoring the fact that wind turbines help me to bring food on the table every night.

To add insult to injury, in the emails they often ask me support to confirm some pseudoscientific “facts” about wind turbines.

I’ve collected some of them in this post – other are coming from anti-wind energy propaganda websites that I read on the subway when I’m bored to discover new, unexpected effect of windmills.

Some of them are similar to the urban legend of the albino alligator in the sewers of New York.

Feel free to contribute!

5. Wind farms causes bush fires. Well, it’s true that (very, very infrequently) a wind turbine burns somewhere. But to say that they are burning woods and bushes it’s a bit too much.

4. The foundations are poisoning the water. Unless you pump 1 million cubic meters of bentonite to do a piled foundation nothing will happen to the water – a foundation is basically only a big stone.

3. The turbine is scaring the fishes – I’m not fishing as much as before. This is courtesy of a fisherman in Juchitan de Zaragoza (Oaxaca, Mexico). I doubt that a fish 10 meters underwater can really hear a WTG.

2. You need more energy to build a wind farm than the energy produced by the turbines. I’ve seen several (serious, scientific) papers on the subject. The energetic payback is usually only a few months.

And the winner is...

1. Wind farms change the weather locally. I love this one. The theory is that, slowing the wind, wind farms modify somehow the climate in the area – some urban legends say that they warm it, some others that they make it more foggy. Well, at least here in norther Germany where I’m living they are not making it any warmer.