Invasive alien plants as an alternative resource for concrete production – multi-scale optimization including carbon compensation, cleared land and saved water runoff in South Africa
Today’s cities are ever-growing, especially in the Global South, inducing massive construction activity. To satisfy these needs we need feasible and environmentally sustainable construction materials, the use of local solutions and, if possible, to enable synergies between sectors for maximum environmental benefit. In South Africa and beyond, invasive alien plants are threatening the indigenous ecosystem while exacerbating water security by affecting water surface runoff and fueling wildfires that release carbon to the atmosphere. The literature suggests that bio-based construction materials can turn buildings into carbon pools. However, the dynamics of using bio-based materials at the urban scale are not yet well known. This paper tests a new type of non-structural bio-concrete, using invasive alien wood chips as a substitute for sand and gravel as aggregates, for future residential construction in Cape Town, comparing this new material to conventional and to earth-based materials, and benchmarking different policy scenarios. Firstly, the material is optimized within technical possibilities achieving the capture of 897 kg of CO2 equivalents per m³. Secondly, a reverse-engineered approach is employed to uncover the limitations of the material. Additionally, C02 emissions from cradle to gate and additional land and water use benefits are analyzed, considering spatial dynamics for transportation impacts. The optimized mix design using invasive alien plants as an alternative resource, combined with a policy that promotes multi-story buildings, offers great potential to achieve near carbon neutral cities, clearing land of invasive alien plants and thus saving annual water surface runoff.
With global demand for building sand tripling in the last 20 years, unregulated sand mining is decimating rivers and coastlines in the developing world, enabled by political corruption and “sand mafias”.
This article outlines the contours of the problem and records new attempts to find sustainable substitutes for use in concrete.
As our “sand budget” heads into the red, there are even calls to begin designing concrete out as a default construction material.
Earth is becoming increasingly popular in contemporary architecture.
Hundreds of projects of high aesthetic and technical quality are emerging across five continents. This material, which has low embodied energy, is readily available and appropriate for participatory buildings.
It could help provide a solution to the needs for ecological and economical housing.
To enable both professionals and the general public to fully appreciate this building material, the following partners have taken the initiative, under the auspices of the UNESCO Chair “Earthen architecture, construction cultures and sustainable development”, to launch the first international prize for contemporary earthen architecture: the CRAterre-AE&CC-ENSAG Laboratory, amàco, les Grands Ateliers, and EcologiK/EK magazine.
Wang Shu, 2012 Pritzker architecture prize laureate, is the president of honour of this TERRA Award, the trophies for which will be presented in Lyon on July 14, 2016 at the Terra 2016 World Congress.
The use of cement and concrete, among the most widely used man-made materials, is under scrutiny. Owing to their large-scale use, production of cement and concrete results in substantial emission of greenhouse gases and places strain on the availability of natural resources, such as water.
The climate crisis is urging us to act fast. Buildings are a key leverage point to reduce greenhouse gas (GHG) emissions, but the embodied emissions related with their construction remain often the hidden challenge of any ambitious policy. Considering that a complete material substitution is not possible, we explore in this paper a material GHG compensation where fast-growing bio-based insulation materials are used to compensate building elements that necessarily release GHG. Looking for analogies with other human activities, different material diets as well as different building typologies are modelled to assess the consequences in term of bio-based insulation requirement to reach climate-neutrality. The material diets are defined according to the gradual use of herbaceous materials, from the insulation up to the structural level: omnivorous, vegetarian and vegan. Our results show the relationship in terms of volume between the climate intensive materials and the climate-negative ones needed to neutralize the overall building GHG emissions. Moreover, they suggest how climate-neutral building can look like and that it is possible to have climate-neutral buildings with wall thickness within the range of current construction practices.
Life cycle assessment (LCA) is widely used to quantify the environmental performance of buildings. Recently, the potential temporal variations in the lifetime of buildings and their influences on assessment results have attracted considerable attention. Dynamic LCA (DLCA) is an emerging research topic. This study provides an overview of the current scenario of DLCA studies in the building field. A literature survey was conducted by searching through scientific literature databases; 48 articles met the inclusion criteria. Eleven dynamic variables as well as their addressing approaches were summarized and analyzed. A few typical dynamic assessment models were synthesized and compared to present the methodology progress. Finally, considering the existing limitations, a few research directions were recommended: setting cutoff criteria for dynamic variables, developing a dynamic database, and considering the interactions between dynamic variables.
This study aims to present a framework to quantify the climate change impact during the buildings’ life cycle. The proposed framework is tested on a bamboo bio-concrete (BBC) building and compared with conventional constructive systems, in a Brazilian housing project considering six cities using Dynamic Life Cycle Assessment (DLCA) and thermal energy simulation.
Biological stabilisers in Earthen Construction: A mechanistic understanding of their response to water-ingress
Earthen construction is regaining popularity as an ecological and economical alternative to contemporary building materials. While building with earth offers several benefits, its performance due to water ingress is a concern for its widespread application. This limitation is often solved by adding chemical stabilisers such as Portland cement and hydraulic lime. Chemical stabilisers are a subject of widespread debate as they increase the cost and embodied energy of the structure, and reduce the desirable characteristics of raw or unstabilised earth.
Construction is considered as one of the most relevant sectors in terms of environmental impacts, due to the significant use of raw materials, fossil energy consumption and the consequent Greenhouse Gases emissions. The use of unconventional and environmentally-friendly materials and technologies is worldwide recognised as a key factor to enable the decrease of material and energy consumption in buildings. Between natural/sustainable materials, those using hemp products and by-products (fibres and hurds) have rapidly widened their field of application in the building industry, mainly because of their good hygrothermal and acoustic insulation properties. Moreover, the usage of these materials allows high carbon storage due to the CO2 sequestration during the agricultural phase.
Reducing the embodied carbon of reinforced concrete structures is crucial to mitigate climate change. Several stakeholders in the construction value chain can contribute to this effort. Therefore, this work quantifies the influence of various decisions made by different stakeholders on the global warming potential (GWP) of a reinforced concrete structure. These decisions include the structural design, material embodied impact, transportation distances, and construction practices. Herein, each decision is modelled as an uncertainty source and its contribution to the total uncertainty of the structure’s GWP is assessed. Two scenarios are considered: business-as-usual, which only considers conventional concrete mix design, and an innovation scenario, which also considers the option of high-filler low-water concrete.
Early design phase energy predictions using a semi-dynamic approach as an accurate proxy for dynamic energy simulations
The building sector is well known as one of the significant contributors to climate change. The use of materials and energy are important drivers, both during construction and the whole life cycle. This study is part of a research to improve the Belgian national approach of life cycle environmental assessment for buildings. The current approach focusses mainly on material use, and the operational energy is estimated via the equivalent degree day method assuming a fixed value of 1200 equivalent heating degree days per year. This paper extends this widespread degree day approach to improve its accuracy by including the effect of various parameters (climate, building characteristics, obstructions by the environment, occupant behaviour).
Life Cycle Assessment (LCA) has become a widely accepted method for environmental assessment of buildings, but is still not commonly applied in design practice. The biggest potential for optimization and reduction of GHG emissions lies in the early stages of the design process. Therefore, a design-integrated approach for LCA is needed. The goal of this paper is to describe the development of a parametric LCA tool for application in early design stages in the Swiss context. The envisioned users of the tool are primarily architecture and engineering students, but also practitioners. The integration of LCA throughout the design process is solved through a modular strategy. In the early stage, pre-defined components are selected to model a complete LCA. In the following design steps when more information is available, individual materials can be input with higher level of detail. The Bombyx tool is developed as a plugin for Grasshopper based on Rhinoceros3D and includes an SQL material and component database. Users are able to choose different materials and building systems and quickly modify the building’s geometry while continuously receiving the calculated environmental impact in real-time. Visualization of the results, e.g. colour code indicate how the design performs in relation to a benchmark or optimization potential. The project is developed in open source to broaden the user and developer community and foster new ideas, designs and implementations in Bombyx.
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Towards a net-zero future
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Every one of us can help limit global warming and take care of our planet. By making choices that have less harmful effects on the environment, we can be part of the solution and influence change.
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