operation oaxaca: pay up.

the economics, part two. (033)

Carlos Manuel Jarquín Sánchez
8 min readApr 1, 2024

this is carlos.

this is part two of me proving myself that i was wrong…

about metal/mineral filtration being the most profitable product.

i explained the chemistry and the tests required for acid mine drainage (AMD) to enter the marketplace.

this is the article.

read it before this one, so everything makes sense to you.

and it is promising.

but one word determines if this can be a genuine solution:


proof: economics.

let’s show you.

when it comes to AMD dry sludge into cement, there are two hurdles:

one: adoption of new alternative materials.

it’s hard to force someone to change their ways… especially if that method is doing well for them, economically.

but let’s be honest.

cement/concrete accounts for 08% of all CO2 emissions worldwide.

during the calcination of cement… the amount of CO2 emitted is between 425 kg CO2/ton — 522 kg CO2/ton.

~60% of CO2 emissions come from the calcination.

the remaining ~35% come from the fuel selection to heat & combust the cement kiln to make the final product.

standard cement kiln.

calcination → calcium carbonate (limestone) will be converted into calcium oxide (lime). this calcium oxide will be used to make clinker… which has the four materials needed in cement:

  • C3S, tricalcium silicate
  • C2S, dicalcium silicate
  • C3A, tricalcium aluminate
  • C4AF, tetracalcium aluminoferrite

so for the cement industry to adopt the new material…we’ll need to meet some end-user requirements.

here are some that i know right off the bat:

  • chemical/physical/mechanical composition of dry AMD sludge.
  • composition of iron, calcium, and aluminum in the dry AMD sludge.
  • how much can dry AMD sludge reduce CO2 emissions?
  • transportation costs from AMD treatment facility to cement plant.

because this brings me to the 2nd point:

two: the only way to enter the cement industry is by selling materials or selling cement/concrete. ~~ gurinder nagra, ceo of furno materials.


there are monopolies.

so i must have something unique to offer for me to have a piece of the pie…the market.

but how big is the pie?

the market size for AMD sludge and portland cement is as follows…

in 2023, the market size for portland cement via the portland cement association was $4.37 billion, USD.

the compound annual growth rate (CAGR) is 4.7%,

and the valuation of the market by 2033 is $6.92 billion, USD.

ok… but how do the cement plants judge their quality?

a material with more iron in it will have a higher price tag than a material with less iron.

specifically, ferric iron (Fe³⁺).

and the material(s) are priced by the short ton.

short ton = 2000 lbs/907.18 kg.

so if a material can lower emissions, operation costs (i.e. electricity, heat, labor), or transportation… it would be worth between $27 — $41/short ton.

the reason why a material with more iron is sought after in cement production is because:

the iron quanity in the raw materials affects the quality of the final cement.

this iron is found in C4AF, one of the materials in clinker.

cement with a lot of C4AF in its cement production involves less energy consumption & CO2 emissions compared to traditional Portland cement due to the lower calcium content and reduced clinkering temperature.

  • this can include a lower carbon footprint.
  • an increased sulfate resistance (for type five portland cement)

but still…

why do cements with a lot of C4AF (tetracalcium aluminoferrite) in its cement production involves less energy consumption & CO2 emissions because due to the lower calcium content and reduced clinkering temperature? (unlike traditional portland cement)

  • the C4AF phase in cement clinker has a lower calcium content compared to the main calcium silicate phases (C3S and C2S).
  • this lower calcium content means less limestone (CaCO3) must be calcined to produce the clinker, reducing the CO2 emissions from the calcination process.

and when portland cement achieves a high iron content…

the clinker production temperature can be decreased to 1350°C from the typical 1450°C when the ferrite content is increased to 9.4% by weight at the expense of belite content in the resulting clinker.

alite → (C3S), tricalcium silicate

belite → (C2S), dicalcium silicate

aluminate → (C3A), tricalcium aluminate

ferrite → (C4AF), tetracalcium aluminoferrite

the lower temperature is achieved because the formation of the ‘melt phase’ during clinkering appears at lower temperatures.

iron enhances alite formation.

this is seen by the lower content/absence of free lime at lower clinkering temperatures.

on top of that…

most of the transition metals in the cement are found in the ferrite phase… notably titanium, manganese and zinc.

there is a good amount of magnesium and silicon….

so oxides other than CaO, Al2O3 & Fe2O3 often make up ~15% of the mass of the calcium aluminoferrite.

this substitution reduces the C4AF melting point to around 1350°C.

so other elements can lower it… if more iron is present.

iron can enhance the overall thermal efficiency of the cement production process.

the melting point of iron is 2800°F or 1538°C.

calcium is 1548°F or 842°C.

silicon is 2577°F or 1414°C.

zinc is 787.2°F or 419.5°C.

so the rest of the elements melt, but iron will hold onto that thermal energy.

it will stand strong.

so more ferric iron/ferrite, less emissions, less energy, less fuel for combustion in clinker, less limestone, etc.

to summarize:

ferric iron in calcium aluminoferrite is necessary for cement to do the following:

  • lower the production temperature of cement clinker & improve the burnability & reaction through melt/flux formation.
  • to meet valorization and landfill diversion targets to use iron-bearing by-products.
  • to limit the tricalcium aluminate content (C3A)… so we can increase the sulfate resistance of the cement.

cool, so we know that we must increase the amount of ferrite/ferric iron in our AMD sludge.

but what good will that do?

there was this tweet that makes sense to what i am building:

…and the only way i can turn this sludge into worth will be either:

  • save cement plants money.
  • save cement plants attention/time.

the former makes more sense than the latter.

and finding raw alternative materials with more ferric iron will allow cement plants to save more money on their energy costs, operational costs, and limestone costs.

the only concern now will be transporting this material from the AMD treatment plant to the cement production.

so the easiest way to lower the cost of transporting is by drying the sludge to the max… and only transporting the solid material.


the cheaper cement plants can produce cement, the more revenue can be applied toward:

  • increased production capacity
  • acquisition of smaller cement plants

p.s. → it’s why CAGR is low in the cement industry. cement is a fine-tuned market and larger corporations can acquire smaller cement plants.

it’s why the larger cement plants can cost $300 million — USD 1 billion.

so the more cement/concrete one sells, it will help to offset the cost of these plants… considering that there must be demand for large quantities of cement in the area.

and another catch is this…

not all portland cement is equal.

there are five types of portland cement according the american society for testing and materials (ASTM).

so each cement plant will have its own needs for the quality and quantity of a raw alternative material…


the amount of calcium aluminoferrite needed for the cement clinker phase.

so i must go into more niche and pick one type of portland cement to enter a market.

so either i will:

  • sell iron-rich dry AMD sludge to cement plants.


  • sell my own cement with AMD sludge <> cement.

but how much of the sintered AMD sludge should go into cement?

1%?, 3%, 5%, 10%? what’s the max i can go without a loss in cement properties, like compressive strength?

sinter → forming a new solid mass of material by pressure or heat without melting it to the point of liquefaction.

the big jigsaw piece.

this is the economic consideration i must beat for dry AMD sludge to win:

blast furnace slag. [BFS]

BFS cement is a mixture of ordinary portland cement & fine-granulated blast furnace slag obtained as a byproduct in the manufacture of steel… but cement has 70% more of BFS than steel.

the BFS cement made in portland cement is known as:

ground granulated blast furnace slag cement [GGBFS].

GGBFS is a fine, glassy granule that contains ‘cementitious’ properties.

GGBFS is obtained as a byproduct in the extraction of iron ore.

the process of iron extraction is via the blast furnace.

a blast furnace is used for making steel, btw.

and the cement plants used the slag (waste) that is rich in iron for their cement production.


the slag that the iron ore obtains is separated & cooled down slowly.

this reacts in a non-reactive crystalline material.

and this is what GGBFS is made of:

SiO2 (silicon dioxide) → 27% — 39% by mass.

CaO (calcium oxide) → 38% — 50% by mass.

Al2O3 (aluminum oxide) → 08% — 20% by mass.

MgO (magnesium oxide) → <10% by mass.

and this slag is grounded finely as that of cement & mixed in the proportion as per the requirements of the desired outcome.

and now, to insert the iron…

because BFS is now a non-metallic coproduct produced in the process of creating iron via limestone usage.

and the BFS is molten when the iron processing barely finishes.

the molten BFS has ~20% — 24% by mass of iron production.

and the way we can cool down the slag is by turning this BFS into GGBFS.

…and this is how the steel by-product can be used as an alternative raw material for cement clinker production.

so this is what i must do to win.

for me to create dry AMD sludge into an alternative cement production:

i need two things to be economically competitive:

  1. increase the ferric iron content to over >33% by mass.
  2. lower transportation costs so we can sell sludge for ~ USD 25/short ton.

but for transportation costs? how far (in miles) will be the cutoff before transportation costs lower the value of utilizing AMD sludge?

15 miles? 20 miles? 40 miles?

the environmental benefits are already there, duh.

so now…

i need to speak with some cement companies/plants and validate some assumptions.

then decide which portland cement i want to focus on. (type I, II, III, IV, V)

and then, how will i make this dry sludge lol…

figure it out.


characterization of iron-rich cementitious materials.

sustainable iron-rich cement: raw material sources and binder types.

© 2024–2100 by Carlos Manuel Jarquín Sánchez. All Rights Reserved.