Soil Pulverizer: Prototype 1 Complete

In preparation for CEB construction – and in particular for the Vault Construction Workshop introduced in the last post, here is the soil pulverizer construction and testing of our first prototype. We started on the drawing board:

and moved on to reality as an attachment for LifeTrac:


Open Source Soil Pulverizer from Marcin Jakubowski on Vimeo.

We found out last year that one of the biggest issues for the success of CEB construction is effective soil preparation. A big part of this is pulverizing the soil to sub-centimeter size. Last year, we struggled on this part – first with digging the soil with the toothbar bucket and then using small rototillers to work through our piles of earth. Many times, the soil was too wet, and sometimes it was too dry. At all times, the time requirement for pulverizing soil was a significant workflow bottleneck which added approximately 1 extra week of time to the brick pressing period.

The results with the soil pulverizer are encouraging. It is not short of power for exploding earth into powder, as you can see in the video. The driving motor is rated for 25 hp. The pulverizer is effective with dry soil, and it even works in wet soil. That’s a great benefit – as many times there are delays due to the weather. The last scene in the video was a taken with the pulverizer working on wet clay. It works nearly or just as well as in dry conditions – because of the rapid rotation and small tine surface. The rotation speed is 500 rpm, and the tines are straight – which combines to small but fast bites through the soil, wet or dry. Each of these small bites contribute effectively to loosening a small piece of clay. With 12 tine sets and 8 effective teeth per tine set, this combines to about 25,000 bites per minute.

The results of operation in wet clay are shown in the last scene in the video. This was wet clay from another location after rain. You can see that the clumps are a little larger, but still around 1 centimeter.

Next, we will have to come up with an effective workflow design for the soil pulverizing part of the operation. It seems that the best route would be to have a tractor loader bucket right behind the pulverizer, so the pulverization-digging step would occur as one step. This is what we suggested earlier this year, and this proposition sounds realistic.

Combining pulverizing and digging into one step means that we avoid digging up large earth piles, but instead, we would work continuously from the ground straight into the hopper of the CEB press. This has the advantage of optimizing workflow ergonomics for brick pressing. The disadvantage to this would be the requirement for a significant soil pulverization working area, perhaps 25×100 feet, so that the exposed layers of earth would have sufficient time to dry for successive passes with the pulverizer. It is wise to turn this digging area into some useful landscaping feature of the finished site

We’d be very happy with 2000 bricks per 8 hour work day – or 4 bricks per minute – with a 3 person team. Right now, we’ll be lucky if we get the CEB automation done in time – so we’ll need 1 person as soil pulverizer operator, 1 person to run the machine, and one person to stack bricks on pallets. Then, the pallets or the machine will have to be moved periodically – and this is where a rear-mounted forklift would be really useful to have for LifeTrac – so that we can either pulverize soil or move pallets with LifeTrac at the same time. Looks like we just added another piece of equipment to our shopping list – to be done by the Vault workshop.

The shopping list of equipment that we are aiming for by workshop time is therefore:

  1. CEB press Prototype 2 – The Liberator 2
  2. Soil pulverizer – done, but needs further workflow integration
  3. MicroTrac as a power source, and possibly for moving Liberator 2 from place to place
  4. 100+ gallon slurry mixer vat and slurry mixer auger for preparing soil mortar
  5. Forklift attachment for moving pallets
  6. Dump trailer for moving excavated foundation soil
  7. Mud sprayer – for finishing wall
  8. Wheel chains on LifeTrac for improved traction

Did I forget anything? Items 1 and 4-8 need to be done. Items 1 and 4 are critical. Gotta go.


  1. Nick

    Wow great tiller! The video music cracks me up, makes me feel like I’m watching Gladiator. Perhaps though it is fitting since it is part of the OSE epic.

    I’m curious about why you need a slurry mixer vat. I spoke with the midwest earth builders at the MREA fair and they get by with some lime as an additive. Are you thinking of doing an earth mortar mix?

  2. Marcin

    Nick, when you were here, we used cement for mortar because we couldn’t use earth mortar in the freezing weather. We really want to do earth mortar, which is the standard in earth construction – so we need to be mixing large quantities of it. Mixing requires a lot of work until the soil turns to a consistency of pudding.

  3. Rasmus

    Looks great, but this demo was done on topsoil. A demonstration on wet, clayey subsoil (what we need for CEBs) would be helpful.

    I can think of other applications for this thing, such as aluminum extraction from clay or for turning rows of (worm-)compost (slow speed please – the worms !)

    Powderized clay (and I mean really powderized, not just sub-centimeter) has useful applications, such as seedball production. Background on seedballs:

  4. […] the high-performance, hydraulically-driven CEB machine, a tractor-loader, walk-behind tractor, soil pulverizer, slurry mixer, and backhoe. We are engaging this entire process from the open source approach in […]