University of Southern California – Graduate School of Engineering “Life Cycle Analysis – Ferrock”

In April of 2017, four graduate students in Environmental Engineering at the University of Southern California (USC) performed a Life Cycle Analysis of Ferrock versus the industry standard Portland cement.  A Life Cycle Analysis as defined by this study is the measurement of all inputs of material, energy as well as the resulting environmental impact that go into the production and delivery of a material – in this case Ferrock and Portland cement.   The results are astonishing both in terms of the superior physical and material qualities and cost of Ferrock but also and most strikingly, the environmental or “green footprint’.

Whereas for each metric tonne of Portland cement approximately +1074 Kg CO2-eq is created versus a carbon-negative footprint for Ferrock of  -50 Kg CO2-eq.

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­­Ferrock:

A Life Cycle Comparison to Ordinary Portland Cement

­­

USC-Cvr Pg Photo

Authors: Alejandro Lanuza,   Ashik Thithira Achaiah,   John Bello, and  Thomas Donovan
April 24, 2017
ISE 576 – Industrial Ecology

 

FERROCK: A LIFE CYCLE COMPARISON TO ORDINARY PORTLAND CEMENT

Alejandro Lanuza Garcia1, Ashik Thithira Achaiah2, John Bello3, and Thomas Donovan4

1M.S. Civil Engineer, M.S. candidate Green Technologies, Fulbright Scholar

Viterbi School of Engineering, University of Southern California, CA. email: lanuzaga@usc.edu

2B.S. Electric and Electronics Engineering, M.S. candidate Green Technologies,

Viterbi School of Engineering, University of Southern California, CA. email: thithira@usc.edu

3B.S. Physical Science, M.S. candidate Green Technologies, Sustainability Engineer, Skanska USA Civil

Viterbi School of Engineering, University of Southern California, CA. email: john.bello@skanska.com

4B.S. Business Administration, GRCT candidate Sustainability & Business,

Marshal School of Business, University of Southern California, CA. email: tdtomdonovan@gmail.com

ABSTRACT

Cement production currently constitutes the fourth largest source of anthropogenic carbon emissions. As these emissions continue to rise, the natural world faces the threat of an unprecedented environmental catastrophe. Ferrock, an innovative iron-based binding compound, presents a carbon-negative alternative to cement that utilizes a variety of waste streams to produce a versatile building material. In this paper, Life Cycle Analysis (LCA) is used from a cradle-to-gate perspective to compare the environmental impacts of Ferrock and Ordinary Portland Cement (OPC), focusing specifically on their contribution to carbon pollution, water use and energy consumption. This process-based LCA includes a comprehensive literature review, and an in-depth environmental assessment of Ferrock production, from the point of its raw materials extraction, to its curing and hardening phase, and all processing steps in between. The results have been compared to a previous life-cycle analysis of OPC. This preliminary analysis finds that Ferrock has both the intriguing potential to replace OPC, and contribute significantly to the promotion of an environmentally sustainable future.

Key words: Ferrock, Life Cycle Analysis, Iron-based binder, carbon negative, recycled by-product

  1. INTRODUCTION

Globally, cement production in 2015 accounted for approximately 8% of total carbon dioxide (CO2) emissions [1]. The world’s infatuation with carbon-intensive materials and processes has grown to be a real pandemic as the accumulation of these emissions contributes to the growing threat of Global Climate Change. Historically, concrete has been an essential factor in the exponential growth of the world’s major cities and continues to be the product of choice for further industrial expansion. However, as researchers are exposing more information about the environmental degradation associated with concrete production, contractors have been forced to reevaluate alternative building materials in order to maintain competitive advantage in an evolving green market. Ferrock is an iron-based compound made of 95% recycled materials that have been proven to be less-expensive, stronger and more flexible in its building applications than OPC. Furthermore, this unique material uses compressed carbon dioxide to expedite the curing process and requires no added heat to catalyze its chemical reaction, making it a carbon-negative alternative to OPC.

  1. CURRENT LITERATURE

Since Ferrock is still a proprietary blend, much of the literature describing its processes and impacts is written from a preliminary perspective. However, the information that is available highlights several beneficial properties for this material. The first of two white-papers drafted by the product’s founder, Dr. David Stone, in conjunction with several engineers from Arizona State University, define the flexural strength and overall durability of the compound compared to OPC. They concluded, “the fracture toughness and critical crack tip opening displacement (CTODC) of the iron-based binders were significantly higher than those of the OPC matrices [8].” Porosity is also another beneficial characteristic of the iron-based material in contrast to OPC, which can be reviewed in Dr. Stone’s second white paper titled, Pore- and Micro-structural Characterization of a Novel Structural Binder based on Iron Carbonation [9]. Additional information regarding the benefits of using recycled materials as substitute ingredients for binding material production are further defined in a short essay by the Environmental Protection Agency titled, Creating a Carbon-Negative Building Material from Recycled Glass, Steel Dust, and Carbon Dioxide [6].

All ingredients necessary for Ferrock production are conventional industrial materials except for iron powder. The main source of literature for fly ash and metakaolin used for this study is a scientific report titled, Sustainability of Construction Materials [4], specifically chapter 17 because of its focus on clinker material production. Chapter 17 makes a comprehensive review of the technical characteristics of composite cements and other low clinker cement mixtures, as well as its components. It also includes a review of the emissions associated to these materials. Information about the environmental impact of limestone has been obtained from the limestone material fact sheet published by the Natural Stone Council [15], which covers a review of the products, applications, performance, physical properties, and environmental data about this material. An additional study by Rod Jones, Michael McCarthy and Moray Newlands [14], was also used for more general information on the environmental impacts of limestone, metakaolin and fly ash in terms of GWP, water and energy use.

Research literature for Ordinary Portland Cement is much more widely available because of it’s longevity amongst the general market [2, 3, 5, 7, 12, 14, 17]. In addition, the components of OPC are also conventional materials that have been thoroughly analyzed, making their statistical data readily available. More information regarding the current literature for Ferrock and OPC can be found by reviewing section 8.0 REFERENCE of this study.

 

IDENTIFICATION OF KEY TECHNOLOGIES

3.1. MANUFACTURING PROCEDURE

Although the structural applications for both materials are very similar, the manufacturing and chemical processes involved are vastly different. Cement is produced by first mining clay and limestone from rock quarries, using explosives to blast the raw material loose from the earth. The material is then hauled to a crushing facility where it is pulverized into 1-½” rocks and blended into a homogenized mixture. The mixture is temporarily stored and then hauled to a milling factory where the size is reduced to a fine powder. The raw blend is then loaded into a kiln, fired at 1400 degrees Celsius and undergoes a chemical reaction, known as calcination. On a molecular level, the calcium carbonate (CaCO3), found in the limestone, begins to decompose at a high heat, releasing carbon dioxide (CO2). In the final stage, the heated mixture is sent through a second stage of milling, in which gypsum is added to extend setting time and then sent to a storage facility where it will be stored until it is shipped to the consumer [7]. At this stage, cement is primarily used for concrete production, which results from the mixing of cement, water and aggregates in the necessary proportions. The combination of cement with water results in an exothermic reaction due to the hydration of the principal chemical components of cement, namely, tricalcium (Ca3) and dicalcium silicate (Ca2SiO4), tricalcium aluminate (Ca3AI2O6), and tetracalcium aluminoferrite (Ca4AI2Fe2O10). These hydrated components harden into a binding material that acts as an agglutinant for the mineral structure formed by the aggregates. Cement also finds its application as a soil stabilizer in geotechnical engineering, and stabilizer for environmental applications [2].

In comparison, Ferrock also uses clay and limestone as part of its composition, but the ratio of clay and limestone used is much smaller compared to OPC, eight and ten percent respectively. The majority of the mixture, totaling 80%, is composed of low-value waste products. The main ingredient is metallic iron powder, which is a by-product of shot blasting, a finishing technique for steel manufacturing. During the shot blasting process the iron powder is ground to a micro-particle scale (~19.03µm) [9], which becomes a considerable nuisance to the blasting facility because of its ineffectual applicability and the inherent respiratory hazard associated with working with such a fine material. These ingredients are combined as a dry-mix with a source of silica, such as fly ash or recycled glass [6]. Oxalic acid is also added to facilitate the chemical process and then blended to create a uniform mixture.

It is necessary to point out that the Oxalic Acid, while small in percentage, represents an important ingredient of the mixture since it promotes the precipitation and mineralization of iron. It is in fact a well-known chemical promoter commonly used in the iron industry due to its characteristics as an iron dissolvent, which prevents oxidization and has the capacity to absorb CO2 (by creating iron oxalate). While reacting with the Ferrock mixture, it chemically reacts with the compound and transforms it into a bonded carbonate molecule and therefore has no further threat as an emitting greenhouse gas (GHG) [13].With the introduction of additional aggregates, water and compressed carbon dioxide, the iron oxide begins to chemically react yielding a new compound, iron carbonate, and emits hydrogen gas as a by-product [8].

Summary of Raw Materials Required For Ferrock Manufacturing

Material Percent  (by weight)[8] Specification/Comments [9]
Iron Powder 60% Waste metallic iron powder with a median particle size of 19.03 µm
Fly Ash or Glass 20% Class F fly ash conforming to ASTM C 618 or Ground glass particles
Limestone 10% Limestone powder (median particle size of 0.7 µm) conforming to ASTM C 568
Metakaolin 8% Conforming to ASTM C 618
Weak organic acid 2% Oxalic acid has been used in previous research as catalyst

 

Note 1: Water-to-solids ratio (w/s) of 0.24, with a range of 0.18 to 0.30, serving mainly as an agent of mass-transfer and does not chemically participate in the reaction.

Note 2: Fully cured samples contain between 8% and 11% of captured CO2 by weight [8, 9].

The following system diagrams represent the manufacturing process for each material. It represents a visual model of the components and their interactions. The arrows represent the flow of mass, energy and the effluent by-products at each stage of the manufacturing process.

 

System Diagram: Ordinary Portland Cement

USC OPC Diagram Flow

 

System Diagram: Ferrock

USC Ferrock Diagram Flow

 

Material Flow Diagram

(Comparison for the production of 1 tonne of cured Ordinary Portland Cement and Ferrock)

USC Material Flow Diagram

Note: Ordinary Portland Cement material flow diagram adapted from [3]

 

3.2. TECHNICAL CHARACTERISTICS

Besides its unique chemical properties as a carbon sink that emits valuable hydrogen gas as a byproduct, Ferrock additionally presents technical characteristics that have potential to make it a promising substitute for cement. Ferrock has similar functional properties in terms of its fresh-state behavior and workability. In addition, the iron-based binder requires a fractional amount of time to cure compared to OPC; 4 days of carbonation compared to the 28 days of hydration that is required for cement to cure. The curing process for Ferrock also has the theoretical potential to be further expedited based on the purity of the compressed carbon dioxide.

From the performance perspective, compressive and flexural strength tests show the pure paste (without aggregate) to be stronger than comparable samples of OPC. In the case of compressive strength, Ferrock shows typical strengths in the range of 5,000 to 7,500 psi, and even as high as 10,000 psi. These values are above the 28-day cured OPC standard values for commercial use (4786 psi for OPC-33 MPa, 6236 psi for OPC-43 MPa and 7687 psi for OPC-53 MPa). Flexural test show Ferrock to have an outstanding flexural response, at a scale of four times stronger than comparable samples of Portland cement. Testing samples of Ferrock paste averaged over 1,200 psi, compared to 275 psi for similar 28-day cured OPC samples, and can be even higher with the addition of glass fibers [8].

Additional characteristics are defined by a comparison with the pore structure of 28-day cured OPC pastes, showing that the overall pore volume was lower in iron-carbonated binders, but the critical pore sizes were larger. This explains that the value of permeability of Ferrock after 4 days of carbonation (k = 2.5 x 10-16 m2) is significantly higher than 28-day cured cement paste (k = 6.17 x 10-20 m2) [9].

Research studies also show that the iron-based binder is chemically stable in marine environments and does not break down upon exposure to salt waters. In fact, results show that Ferrock has the capacity to incorporate some of the salt, especially the chlorine ions into the mineral structure. This trapping capacity seems to extend to some toxic contaminants such as arsenic [10].

3.3. POTENTIAL APPLICATIONS

The characteristics of Ferrock make it an extremely versatile compound. Its applications can vary based on the coarse size of the aggregates added. Using a coarse-grit aggregate it may be used slabs, blocks, other pre-cast forms and general applications. By using fine aggregates the material becomes very malleable and can be spread on like stucco, plaster or mortar. Adding additional reinforcement, like rebar, allows for the construction of large full-sized structures [13]. Like concrete, the applications of this material is limited only by its form. When cast in place, Ferrock’s shorter cure time allows for compressed project construction schedules, conserving capital resources.

While most contemporary building materials must be specially treated to withstand environmental degradation, Ferrock is resistant to rust, oxidation, UV radiation, rotting and corrosion. Therefore, Ferrock can be used for marine applications like breakwater, seawalls, piers, structural pilings, foundations and other structures exposed to seawater. Its environmental durability also makes its application in the manufacture of pipes that are typically used for water transmission and wastewater removal. Ferrock is not affected by the constituents of sewage water like hydrogen sulfide and sulfuric acid, which corrodes regular cement pipes. Further, since Ferrock is less brittle compared to concrete, it enables better pipe-to-pipe connection and consequently there is less damage while aligning and installing sections [27].

In a large-scale application, the plausibility for sizable industrial transformation begins to take form. By constructing buildings, homes, roadways, walkways and various forms of infrastructure out of this material prospective urban-dwellings will become consumers of carbon dioxide compared to the exponential producers of present-day. While architects may quarrel with the ascetic limitations of a rustic pigment covering the majority of urban landscapes, the consequent environmental restoration associated with such an effort may entice designers to find new applications for a variety of red-Ferrock structures.

  1. LIFE-CYCLE ANALYSIS

Life-cycle analysis (LCA) is an evaluation technique used for the assessment of environmental impacts associated to technologies, products or processes. The formal structure of an LCA is defined by the International Organization for Standardization in ISO 14040 and consists of three main sections: goal and scope definition, inventory analysis, and impact analysis [11].

4.1. GOAL AND SCOPE

The goal of this LCA is to compare the environmental impacts of Ferrock and Ordinary Portland Cement in terms of carbon emissions, water and energy use. Using a life-cycle framework, the manufacturing process of Ferrock has been evaluated to assess its impacts on the environment. This analysis was conducted using a similar methodology to that of a pre-existing study on Ordinary Portland Cement [12]. By limiting the dependent variables only to the ingredients and processes involved to make each binding material, the analysis highlights the direct impacts associated with these binding materials. The objective of this approach is to ultimately identify how the use of Ferrock in place of OPC can greatly mitigate the increasing volume of industrial-based carbon dioxide emissions, reduce energy demands for structural material production and limit the consumption of freshwater resources.

The scope of the LCA is from “cradle-to-gate.” It takes into account the environmental impacts of raw materials extraction and processing, transportation, the production processes of the binding materials and the curing and hardening phase. The scope of the LCA is also defined by the functional unit and the system boundary:

4.1.1. FUNCTIONAL UNIT

The functional unit used for this analysis is 1 Metric Tonne of Cured Binding Material.

4.1.2. BOUNDARIES AND LIMITATIONS

Since both Ferrock and cement have a multitude of applications within the construction industry (beams, blocks, pillars, walkways, roadways, houses, bridges, etc.), the product’s use and end-of-life phases are eliminated from this particular assessment to bound the quantity of outstanding variables within an intermediate stage. However, the continuation of this process remains feasible by building on the results of the following assessment.

4.1.3. EXCLUSIONS

The ISO 14041 guidelines [11] suggest that those materials that constitute less than 5% (in weight) of the final product can be excluded from the LCA, if they have a negligible environmental impact. Oxalic Acid constitutes less than 2% of the total composition of Ferrock by mass and is a common acid used in the iron industry. During the manufacturing process the acid is fully incorporated into the chemical structure of Ferrock as a carbonate molecule [13], therefore there is no reasoning to suggest it will have a transcendent environmental impact. As a result of its negligible weight and impacts it will be excluded from this analysis.

In addition, based on the ISO 14041 principles, since iron powder is a low-value industrial by-product the environmental burdens associated with its generation will also be excluded from this study. The consumption of fuel and electricity involved in the upstream processes such as the production of natural gas, environmental impacts and emissions from combustion at coal-fired power plants have been excluded in this study. However, the energy and resources spent in the extraction and processing of raw materials quarrying and electricity generation, and are captured in the background data of the LCA.

Exclusions also include capital equipment, infrastructure and personnel-related activities (travel, furniture and office supplies). These are expected to contribute negligibly (<1%) to the total impact of cement production, given the long lifetime of these items and high output of cement over this period.

4.2. INVENTORY ANALYSIS

The inventory analysis phase, which is further detailed in section 5.0. METHODOLOGY AND ANALYSIS, will highlight the contribution rate for the objective impacts during the production of Ferrock and OPC. This analysis focuses only on the following aspects of the production life-cycle, and is better known as a cradle-to-gate assessment:

  • Extraction and processing of raw materials
  • Transportation of raw materials from source to production site
  • Consumption of energy and water required to produce a hardened metric tonne of cement and Ferrock
  • Emissions generated from producing a hardened metric tonne of cement and Ferrock

 

4.3. IMPACT ANALYSIS

Once all components of each material have been identified and quantified, various impact indicators are used to define the environmental impact of the iron-based binder, which is summarized in section 6.0. RESULTS AND CONCLUSIONS.

 

4.4. QUESTIONS TO ADDRESS

This study addresses the following questions:

  1. What are the environmental impacts of Ferrock?
  2. How does it compare to OPC?
  3. Does this product merit further exploration of industrial scale production?
  4. What are the economic costs, benefits and/or limitations of Ferrock?
  5. What direction should further research take?
  6. METHODOLOGY AND ANALYSIS

The methodology adopted for this study consists of a process-based LCA, in which the carbon emissions, water use and energy use of each stage are analyzed for the raw materials extraction and production, transportation, binder manufacturing and curing phase – as described in 4.1.2 BOUNDARY AND LIMITATIONS. In order to proceed with this analysis a compilation of this information is organized in the life-cycle inventory analysis (LCIA), seen in the tables below.

 

5.1. DATA SOURCES & DATA QUALITY

The LCIA has been built using exhaustive data research. It should be noted that the environmental impact values of each quarry or processing plant are very sensitive to a variety of classifying characteristics, such as their location and the technologies available. Since most suppliers do not disclose in-depth statistical data on the environmental impacts of their products, general data from varying regions has been used to build the LCIA.

 

5.1.1. RAW MATERIALS

The following tables summarize inventory values derived from the referenced resources:

Reported Inventory Values for Ferrock Ingredients

Raw Material GWP[kg CO2-eq/tonne] Energy[MJ/tonne] Water[liters/tonne] Reference
Iron Powder Not considered since it is a waste product of the iron industry
Fly Ash 4* 33.5* 0 [14]
27 (assumption of 100 km of transport)408 [4]
Limestone 32* 45.7* 48* [14]
110 7090 81783 [15]
Metakaolin 330 1440 0 [14]
423330370 [4]
435* 2500* 0* [16]
Oxalic Acid Not included since it represents less than 5%

*Selected values for the LCIA of Ferrock

 

Selected Values for the Life-cycle Inventory Analysis of Ferrock

Raw Material GWP[kg CO2-eq/tonne] Energy[MJ/tonne] Water[liters/tonne]
Iron Powder
Fly Ash 4 33.5 0
Limestone 32 45.7 48
Metakaolin 435 2500 0
Oxalic Acid

 

5.1.2. TRANSPORTATION

Transportation energy intensity is the amount of energy needed to transport each material, based on the transport vehicle’s engine’s energy requirements. The following values have been used to estimate the environmental burden of the transport of raw materials:

Mode Vehicle, fuel (fraction of vehicle) Energy Intensity (KJ/ metric ton-km)
Road Single Unit Dump Truck, Gasoline (0.549) 371
Single Unit Dump Truck, Diesel (0.451) 338
Dry bulk tank truck-tractor, diesel 830
Van, basic enclosed, diesel 539
Rail Locomotive, diesel 249
Waterborne Barge, distillate fuel oil (0.304) 103
Barge, residual fuel oil (0.696) 237

Note 1: Energy intensity table of various modes of transportation adapted from [17].

Note 2: The average CO2-emission factor recommended for road transport operations is 62g CO2/tonne-km. This value is based on an average load factor of 80% of the maximum vehicle payload and 25% of empty running. [20]

Note 3: For deep-sea shipping, the estimated average is 8.4 g CO2/tonne-km for container shipping.[20]

The transportation methods and distances used to get raw materials from the point of extraction to the processing plant are shown in the table below. The estimated distances shown in the table below have been done taking into account the hypothetical location of a manufacturing plant in Long Beach, CA.

 

Transportation Distance of Raw Materials for Ferrock Production

Material Distance [19] Mode of transportation Energy Intensity [KJ/tonne-km] [17] Energy Consumption [MJ/tonne] Carbon Intensity[g CO2/ tonne-km] GWP[Kg CO2/ tonne]
Iron Powder Short/Medium (LA)50-100 km Road 371 18.5-37.1 62 3.1 – 6.2
Fly Ash Medium/Long (CA/AZ)400-1000 Road 371 148.4-371 62 Medium- 24.8Long- 62
Recycled Glass Short (LA)50-100 km Road 371 18.5-37.1 62 Short: 3.1 – 6.2
Limestone Medium (CA)600-700 km Road 371 222.6-259.7 62 37.2 – 43.4
Metakaolin Long (China)11000 km Maritime 103 1133 8.4 92
Oxalic Acid Long (China)11000 km Maritime 103 1133 8.4 92
Carbon Dioxide Local Road2 371 18.5-37.1 62 3.1 – 6.2

 

Note 1: The most likely value inside the ranges will be used for the determination of the environmental impact.

Note 2: The burdens of transporting CO2 cylinders (Local source) will be assumed to be equal to the Iron Powder transportation burdens.

 

5.1.3. MANUFACTURING PROCESSES

The data derived from the manufacturing process of Ferrock is much less energy intensive than OPC because it does not require any heat to catalyze the curing process. Since Ferrock manufacturing only involves the blending and grinding of raw resources, for an industrial-scale manufacturing application the assumption is made that Ferrock will have the same energy values as the “finish grinding and blending” phase of Ordinary Cement production, found in Huntzinger and Eatmon’s journal article, A life-cycle assessment of Portland cement manufacturing: comparing the traditional process with alternative technologies [3]. Based on this report, the associated environmental burden reported for this phase is estimated to be 170.2 MJ/tonne.

5.1.4. CASTING, HARDENING AND CURING

The machinery and methods used to cast an OPC-based structural material, like concrete, and a Ferrock-based structural material are generally the same. However, there are variable differences between the water-solid ratio for each compound and their relationship with CO2. Also, OPC does not produce H2 gas during curing.

Curing Properties

Ferrock OPC
Water-Solid Ratio 0.18 to 0.30 0.40 to 0.70*
CO2 Absorbs CO2 in a ratio of 0.1 tonnes CO2/tonne [8] No relationship during curing
H2 17 kg H2 /tonne produced [13] No relationship during curing

 

*This ratio is very dependent on the workability requirements of the mixture and can be easily altered by using additives to the mix, such as plasticizers or superplasticizers.

5.2. ANALYSIS

The following table shows the results from weighting selected values with the proportions of each material.

Desegregated Environmental Impact Assessment of Ferrock Production

Raw Material GWP[kg CO2-eq/FU] Energy[MJ/FU] Water[liters/FU]
1. RAW MATERIAL PRODUCTION
Iron Powder
Fly Ash 0.72 6.03 0
Limestone 2.88 4.11 4.32
Metakaolin 31.32 180 0
Oxalic Acid
Carbon Dioxide (100) 0 0
2. TRANSPORTATION
Iron Powder 1.67 10 0
Fly Ash 0.56 26.71 0
Limestone 3.9 23.4 0
Metakaolin 6.62 81.57 0
Oxalic Acid 1.66 20.40 0
Carbon Dioxide 0.31 1.85 0
3. MANUFACTURING
Mixing, Casting, Hardening and Curing 0 170.2 216
4. BYPRODUCT GENERATION
Hydrogen 17 (kg H2/FU) (2210)(Energy equivalent of 17 kg H2 [22]) 0
TOTAL
1 FU 49.64-100 = – 50.36 524.34-2210 = -1685.66 220.32

 

David Phillips <dave@nzbuilders.com>Proportional Environmental Impact by Life Cycle Phase for Ferrock

USC Study pg14

5.3. SENSITIVITY ANALYSIS

5.3.1. CASE 1: REPLACING FLY ASH WITH METAKAOLIN

Due to the growing threat of climate change attributed to the cement manufacturing industry, researchers have tested the feasibility for incorporating waste pozzolanic materials and by-products, such as fly ash and slag into the mix design of OPC [23]. However, recent studies have pointed out that less than 20% of the global cement demand can be met using fly ash and slag because of its dwindling supply [16] . This figure will likely decrease below 10% as cement consumption continues to rise and fly ash generation gradually decreases due to contemporary legislation forcing coal-fired power plants to suspend their operations.

Clay based materials such as metakaolin represent a viable alternative to fly ash since its main component is also silica (SiO2) and it is a material that presumably has sufficient reserves to replace a significant proportion of binders [24]. The following sensitivity analysis contrasts the results of using Metakaolin has a direct substitute for fly ash, Ferrock’s second major component.

 

Sensitivity Analysis Case 1

Raw Material Proportion of the Mix in the FU (%) GWP[kg CO2-eq/FU] Energy[MJ/FU] Water[liters/FU]
RAW MATERIAL PRODUCTION
Iron Powder 54
Metakaolin 25.2 109.62 630 0
Limestone 9 2.88 4.11 4.32
Oxalic Acid 1.8
Carbon Dioxide 10 (100) 0 0
TRANSPORTATION
Iron Powder 54 1.67 10 0
Metakaolin 25.2 23.18 285.52 0
Limestone 9 3.9 23.4 0
Oxalic Acid 1.8 1.66 20.40 0
Carbon Dioxide 10 0.31 1.85 0
MANUFACTURING
Mixing, Casting, Hardening and Curing 0 170.2 216
BYPRODUCT GENERATION
Hydrogen 17 (kg H2/FU) (2210)(Energy equivalent of 17 kg H2 [22]) 0

TOTAL

1 FU 143.22 – 100= 43.22 1145.48 – 2210= – 1064.5 220.32

USC Sensitivity Case1 #2

Results show that a substitution of metakaolin for fly ash in the mix design dramatically increases the carbon dioxide emissions, developing a revised binding material that is no longer carbon-negative. There is also an adverse effect on the amount of energy consumed, but the amount of water needed to produce the material remains the same as the original design.

5.3.2. CASE 2: REPLACING FLY ASH WITH RECYCLED GLASS

Raw Material GWP[kg CO2-eq/FU] Energy[MJ/FU] Water[liters/FU]
1. RAW MATERIAL PRODUCTION
Iron Powder
Recycled Glass
Limestone 2.88 4.11 4.32
Metakaolin 31.32 180 0
Oxalic Acid
Carbon Dioxide (100) 0 0
2. TRANSPORTATION
Iron Powder 1.67 10 0
Recycled Glass 0.56 26.71 0
Limestone 3.9 23.4 0
Metakaolin 6.62 81.57 0
Oxalic Acid 1.66 20.40 0
Carbon Dioxide 0.31 1.85 0
3. MANUFACTURING
Mixing, Casting, Hardening and Curing 0 170.2 216
4. BYPRODUCT GENERATION
Hydrogen 17 (kg H2/FU) (2210)(Energy equivalent of 17 kg H2 [22]) 0

TOTAL

1 FU 48.92-100 =- 51.08 518.31-2210 =-1691.69 220.32

USC Sensitivity Case1 #3

Another applied alternative is to replace fly ash with crushed recycled glass. Since they both contain a source of silica the chemical reaction during the carbonation phase remains the same as the original design. The results of this sensitivity analysis are as follows:

Using this alternative mix design the carbon dioxide emissions remain a net-negative product of the manufacturing process, even more so than the original design. The amount used is also reduced using this method, however water consumption remains consistent.

5.3.3 SENSITIVITY ANALYSIS COMPARISON

The following figure shows a comparison of the results:

USC Sensitivity Compare

 

Through this analysis it is concluded that the incorporation of recycled glass has an overall positive contribution to the environmental performance of the binding material. These numbers not only showcase the minimal adverse impact this compound has on the environment, they significantly outperform the environmental figures associated with Ordinary Portland Cement.

 

6.0. COST BENEFIT ANALYSIS (Appendix)

Preliminary version attached as an Appendix.

 

7.0 RESULTS AND CONCLUSIONS

The figures below show the estimated values of performance metrics (energy, water and CO2 emissions) for each binding material.

 

Performance Comparison Between Ferrock and OPC

Parameter Ordinary Portland Cement(per metric tonne of production) [12] Ferrock(per metric tonne of production)
Energy use (Total Primary Energy Consumption) 5887 MJ 557 MJ**
Water* 10,100 L 220 L
Global warming potential 1040 Kg CO2-eq – 50 Kg CO2-eq

 

* These values include the water needed for the curing and hardening phase of the binding materials.

** The manufacturing process of Ferrock generates 17 kg of H2, which has an energy content of 2210 MJ. Therefore, the overall process produces a net of 2210 – 557 = 1653 MJ.

 

 

As the global population continues to rise, driving further industrial expansion, innovative development solutions are critical to maintain proportional growth without compromising social order. This stability is contingent upon the regulation of ecological systems, as they relate to resource availability, economic prosperity and the impact they have on human health. The adverse environmental effects of cement production are among the list of critical development factors in need of such innovation. The energy-intensive manufacturing process of Ordinary Portland Cement contributes significantly to the surging volume of accumulated GHG emissions in the atmosphere and continued natural resource depletion. By introducing Ferrock as a potential alternative to OPC for structural applications these adverse environmental impacts are mitigated to a fractional standard. Due to its unique and encouraging technical characteristics, its versatile applicability and the respectively minimal impact it has on the natural world throughout the first initial stages of the product’s life, it serves as a suitable replacement for Ordinary Portland Cement in the majority of functional applications. Even in its propriety state the quantifiable advantages of using Ferrock have been defined to be extremely enticing, but the ambiguity of its unique properties have the potential to have an even greater influence of the sustainable well-being of the environment and the prosperity of human civilization.

 

8.0 FURTHER RESEARCH

As mentioned, this preliminary report only analyzes a portion of Ferrock’s technical characteristics and chemical properties. Further research is necessary to fully-define the feasibility for widespread integration of this material. Given the emerging nature of this innovative material the long-term durability, especially in terms of its performance reliability in the presence of varying environmental conditions, is still unknown. Since OPC has been used in civil development since primitive ages of industrialization its processes have been refined to account for all environmental variability. Additionally, environmental impacts transpiring from the use and end-of-life phases of the product’s life-cycle should also be further explored to properly identify the full scope of the durability and resilience of this material.

A reevaluation of energy, water and GHG impacts will be necessary once industrial-scale, mature manufacturing processes have been established. The location of a facility this size is best positioned as part of an eco-industrial park, because of the feasible access for its required input waste materials. In terms of by-product synergy a cost neutral exchange of gases is theoretically feasible based on the product’s input needs for carbon dioxide and its production rate of hydrogen gas. The formation of hydrogen gas as a by-product of Ferrock production represents an intriguing opportunity for further applications of this material, especially as the energy industry looks for alternative sources of fuel. The clean-burning nature of hydrogen gas positions it as one of the leading fuels to aid the transition away from fossil-fuel energy sources.

Using a replicable precast methodology the curing environment can be controlled, meaning the opportunity for harvesting the effluent hydrogen becomes more practical. The precast structure could be loaded into a vacuum-sealed chamber where the chemical process is catalyzed by a source of CO2, the emitting H2 gas would then be drawn through the chamber’s ducting and compressed into consumable cylinders [13]. By introducing Ferrock as a potential generating source for this high-value fuel its overall market potential is seemingly limitless.

 

9.0 REFERENCES

[1] Jos G.J. Olivier (PBL), Greet Janssens-Maenhout (EC-JRC), Marilena Muntean (EC-JRC), Jeroen A.H.W. Peters (PBL) (2016). “Trends in Global CO2 emissions: PBL Netherlands Environmental Assessment Agency; PBL publication number: 2315

[2] Versatile Cement. Cement Applications. Accessed April 21, 2017 <http://www.cement.ca/en/Cement -applications. html>

[3] Huntzinger, D. N., & Eatmon, T. D. (2009). “A life-cycle assessment of Portland cement manufacturing: comparing the traditional process with alternative technologies”. Journal of Cleaner Production, 17(7), 668-675. doi:10.1016/j.jclepro.2008.04.007

[4] In Khatib, J. M. (2016). “Sustainability of construction materials. Chapter 17: Low clinker cement as a sustainable construction material”. Cambridge, UK: Woodhead Publishing.

[5] McLellan B.C., Williams R.P., Lay J., Van Riessen A., Corder G.D.”. Costs and carbon emissions for geopolymer pastes in comparison to Ordinary Portland Cement. Journal of Cleaner Production. 19(9-10), 1080-1090 (2011) <http://dx.doi.org/10.1016/j.jclepro.2011.02.010>.

[6] EPA. “Creating a Carbon-Negative Building Material from Recycled Glass, Steel Dust, and Carbon Dioxide (Tohono O’odham Community College)”. 2013-2014 Program Report for Tribal ecoAmbassadors.  Available from: <https://www.epa.gov/tribal/2013-2014-program-report-tribal-ecoambassadors>.

[7] ENGINEERING INTRO. 2012. Cement Manufacturing Process. [ONLINE] Available at: http://www.engineeringintro.com/uncategorized/cement-manufacturing-process/. [Accessed 2 April 2017].

[8] Das S. et al.. “Flexural Fracture Response of a Novel Iron Carbonate Matrix – Glass Fiber Composite and Its Comparison to Portland Cement-based Composites.” Science Direct. Construction and Building Materials, n.d. Web. 27 Feb. 2017.

[9] Das S. et al.. “Pore- and Micro-structural Characterization of a Novel Structural Binder Based on Iron Carbonation.” Science Direct. Materials Characterization, Dec. 2014. Web. 27 Feb. 2017.

[10] Stone, David. “Top Ten List of Characteristics for Ferrock TM —a New Green Building Material”. Unpublished manuscript.

[11] Graedel T.E., Allenby, B.R. “Industrial Ecology and Sustainable Engineering. Chapter 12: Introduction to Life Cycle Assessment ”.2010 Pearsons Education.

[12] EPD for Portland Cements – Industry Wide EPD. ASTM INTERNATIONAL website. Available from: <https://www.astm.org/CERTIFICATION/EpdAndPCRs.html>.

[13] Dr. Stone, D. (2017, April 18). Inventor of Ferrock. Telephone interview.

[14] Jones, R. et al. “Fly Ash Route to Low Embodied CO2 and Implications for Concrete Construction”. 2011 World of Coal Ash (WOCA) Conference -May 9-12, 2011 in Denver, CO, USA.

[15] Natural Stone Council. Limestone Dimensional Stone Quarrying and Processing: A Life-Cycle Inventory. August 2008. Center for Clean Products. The University of Tennessee. <http://isse.utk.edu/ccp/projects/naturalstone/results_pubs.html>.

[16] Health, A.C. et al. “Minimising the global warming potential of clay based geopolymers”Journal of Cleaner Production Volume 78, 1 September 2014, Pages 75–83

[17] Marceau, Medgar L., Nisbet, Michael A., and VanGeem, Martha G. Life Cycle Inventory of Portland Cement Concrete, SN3011, Portland Cement Association, Skokie, Illinois, PCA, 2007, 121 pages.

[18] Alibaba. Accessed April 21, 2017. <https://www.alibaba.com/>.

[19] Google Maps. Accessed April 21, 2017. <https://www.google.com/maps>.

[20] Mckinnon, Guidelines for Measuring and Managing CO2 Emission from Freight Transport Operations, Issue 1, March 2011

[21] Rodrigue, Dr. Jean-Paul. Transport Costs. Accessed April 22, 2017. https://people.hofstra.edu/geotrans/eng/ch7en/conc7en/ch7c3en.html.

[22] Elert, Glenn. “Energy Density of Hydrogen.” Energy Density of Hydrogen – The Physics Factbook. Accessed April 22, 2017. http://hypertextbook.com/facts/2005/MichelleFung.shtml.

[23] Duxson, P., Fernández-Jiménez, A., Provis, J.L., Lukey, G.C., Palomo, A., Deventer, J.S.J., 2007. Geopolymer technology: the current state of the art. J Mater Sci 42, 2917-2933.

[24] Heath, A., Paine, K., Goodhew, S., Lawrence, M., Ramage, M., 2013. The potential for using geopolymer concrete in the UK. Construction Materials 166, 195 -203.

[25] “Showing Results for “cement”.” Cement – Mortar, Cement & Concrete Mix – Concrete, Cement & Masonry – The Home Depot. Accessed April 23, 2017. http://www.homedepot.com/b/Building-Materials-Concrete-Cement-Masonry-Mortar-Cement-Concrete-Mix/Cement/N-5yc1vZbogdZ1z0ueuf/Ntk-SemanticSearch/Ntt-cement?Ntx=mode%2Bmatchall&NCNI-5.

[26] “Hydrogen Production” Multi-Year Research, Development, and Demonstration Plan. 2015 PRODUCTION SECTION

[27] Ironkast (Precedent of Ferrock) .Accessed April 21, 2017.<http://ironkast.com>.

 

APPENDIX

  1. COSTS (Preliminary version)

The manufacturing process of Ferrock is a very simple process, which involves mixing of the raw materials- therefore, most of the costs come from transportation and supply of raw materials. The following table points out possible suppliers for each material, a range of purchase price and an estimate of transportation costs. It should be noted that, as the iron powder is an industrial waste product that is otherwise landfilled, diverting it could be a possible source of income.

 Material  Sourcing [13,  18]  Purchase Price [13,  18]  Transportation Costs [21] Weighted cost for the FU
Iron Powder –        Schnitzer Steel (Northern California (Sacramento/ Oakland)-        Sims Adams (Not found)-        Sand Blasting Sites – e.g. Rancho Cucamungo (Los Angeles area) Earnings $45/tonne
Fly AshOr Recycled Glass –        FA:Coal Plants (California/ Arizona and beyond)-        G:Local recycling facilities (Local) FA:$700/ TonneRG:$0/Tonne FA:$70/TonneRG:$10/Tonne $138.6/tonne
Limestone –        Mountain Gate Quarry (North of Sacramento)-        Imerys $15 / tonne $1.5 / tonne $1.49/tonne
Metakaolin –        Shijiazhuang jinli Mineral Co. Ltd (China)-        Burgess Pigment Co (Georgia) $150-300 /tonne $15-30 /tonne $11.88/tonneTo $23.76/tonne
Oxalic Acid –        Humate (Tianjin) International Limited (Shandong, China)-        WEIFANG HUABO (Qingdao, China) $450-750 /tonne $45-75 /tonne $8.91/tonneTo $14.85/tonne
Carbon Dioxide –        Precast: Symbiosis with a source of CO2-        Cast in-place: Cylinders (local) $28 – 50 lb /tank of CO2Which equals to $1233.5/tonne(rented $8/month) Precast: FreeIn Place: $2.8 – 50 lb /tank of CO2 (rented $0.8/month) Precast: FreeIn Place: $135.7/tonne

Note: Transportation costs have been calculated as a 10% of the total cost of the product [21].

 

6.1 FINANCIAL BENEFITS

There are three possible sources of income for a business based on Ferrock:

  • Selling price: assumed to be the same as cement $195.23/tonne [25]
  • Waste diverted from landfill: Nowadays companies are paying $45/tonne of iron powder landfilled ($24.3/tonne of Ferrock)
  • Selling of Hydrogen: assuming a market price of $6.60 per Kg of H2 [26] ($112.2/tonne of Ferrock)

 

6.2 DISCUSSION ON COST/BENEFIT

The selling price of 1 Tonne of cement is $195.23/tonne [25]. Since Ferrock is a competitor of cement, it will be assumed that the selling price of Ferrock will be the same as cement.

The costs of Ferrock are analyzed in base of different scenarios:

 

Scenario 1: Cast in place (use of CO2 bottles) Scenario 2: Pre-cast manufacturing (free CO2) Scenario 3: Glass powder / Cast in place (No use of fly ash/ use of CO2 bottles) Scenario 4: Glass powder / Pre-cast (No use of fly ash/ free CO2)
Cost $138.6/tonne [FA]+ $1.49/tonne [LM]+ $11.88/tonne to $23.76/tonne [MK]+ $8.91/tonne to $14.85/tonne [OA] + $135.7/tonne [CO2]________________$296.58/tonne to $314.4/tonne $138.6/tonne [FA] +$1.49/tonne [LM]+ $11.88/tonne to $23.76/tonne [MK]+ $8.91/tonne to $14.85/tonne [OA]+ $135.7/tonne________________$160.88/tonne to $178.7/tonne $138.6/tonne [FA] +$1.49/tonne [LM] +$11.88/tonne to $23.76/tonne [MK] +$8.91/tonne to $14.85/tonne [OA] +$135.7/tonne [CO2]_____________________$157.98/tonne to $175.8/tonne $1.49/tonne [LM]+$11.88/tonne to $23.76/tonne [MK]+ $8.91/tonne to $14.85/tonne [OA]+ $135.7/tonne__________________________$22.28/tonne to $40.1/tonne
Benefit $112.2/tonne [H2] +$24.3/tonne [IP] +$195.23/tonne [Ferrock]__________________$331.73/tonne $112.2/tonne [H2] +$24.3/tonne [IP] +$195.23/tonne [Ferrock]________________ $331.73/tonne $112.2/tonne [H2] +$24.3/tonne [IP] +$195.23/tonne [Ferrock]_____________________$331.73/tonne $112.2/tonne [H2]+ $24.3/tonne [IP]+ $195.23/tonne [Ferrock]_________________________$331.73/tonne
Net Margin $17.33/tonne to $35.15/tonne $153.03/tonne to $170.85/tonne $155.93/tonne to $173.75/tonne $291.63/tonne to $309.45/tonne

 

Results show that Ferrock is a product with a great economic potential It should be also noticed that from a Construction Management point of view, the reduction of the curing phase to 4 days would impact the set time of the construction schedule and would reduce the critical path of the construction, with the consequent reduction on building times and costs, which makes it a very desirable product for the construction industry. This characteristic can lead to a price differentiation that can yield to higher selling prices.