Project Summary

(1)      This report describes the work and findings of the student project entitled “Use of Recycled Plastics in Building Materials” submitted for the Green Wave Environmental Care Competition 2009.

(2)      This project utilizes recycled plastics as partial replacement of aggregate ingredients in building blocks for infrastructure, green building and protective structure applications.

(3)      Particular focuses on the construction of a permeable interlocking pavement system for infrastructure application. 

(4)      The innovation and uniqueness of this project include:

▪         A viable technology to reuse large volumes of plastics waste with varying physical and chemical compositions in Singapore and worldwide.

▪         Capitalizing on the advantages of recycled plastics which provide the building materials with enhanced physical and mechanical properties compared to conventional construction materials.

▪         Utilizing a simple production method to fabricate building blocks.

▪         Ensuring chemical inertness and environmental safety through stabilization and solidification of recycled wastes within the building blocks.

(5)      The report is divided into three sections, namely;

           ▪         Part 1: Testing and Selection of Materials
           ▪         Part 2: Development of Prototype
           ▪         Part 3: Applications

Part 1: Testing and Selection of Materials

(6)      The experimental results based on physical properties (mixture homogeneity, hardened density, water absorption), mechanical behaviour (compressive and flexural strengths, modulus of toughness) as well as cost consideration were used as a basis for the development of prototype in the form of a permeable interlocking pavement system in Part 2.

(7)      Mixtures P8, P2, P7 and P3 are most cost-effective due to the low price of recycled plastics used in these mixtures; whereas P4 and P6 are not economically viable due to the high cost of silica fume (SF) in these mixtures.  The use of blast-furnace slag (BFS) in mixture P5 did little to improve the physical and mechanical properties of concrete with recycled plastics, and mixture P1 was too brittle and prone to cracking.

Part 2: Development of Prototype

(8)      The use of recylced plastics to develop and construct prototype for a permeable interlocking pavement system had been succesfully implemented.  Design considerations were based on pavement material, pavement type and pavement layout as follows:

▪            Pavement block
▪            Filled joints
▪            Bedding course
▪            Base material
▪            Geotextile
▪            Pavement type
▪            Pavement layout

(9)      A simple production method using a block-making equipment had been successfully employed to fabricate and mass-produce building blocks of different shapes and sizes incorporating recycled plastics for infrastructure, green building and protective structure applications.

Part 3: Applications

Project Summary

Beverage industries based in Singapore generate large quantities of organic waste.  Local beer breweries generate approximately 15,500 tonnes of spent beer grains (SBG) annually which are wastefully incinerated or delivered to local or overseas farms to be used as animal feed.  The high moisture content of the beer spent grains requires additional precious and limited fossil fuels in order for complete incineration to take place.  This further contributes to the large carbon footprint that Singapore already possesses.  Using the SBG as animal feed is also not an optimal use as they are high in lignocellulose, which are tough for animals to digest.  A more environmentally sustainable method to handle the large amount of nutrient rich BSG is missing in the sustainable waste management equation of BSG in Singapore.

In recent years, an increasing market demand for fresh mushrooms in Singapore has been observed.  The steady increase in the amount of fresh mushrooms imported into Singapore highlights the inability of the local mushroom supplier to meet consumer demands.  Morevover, the limited variety of locally produced mushrooms has resulted in imports of 8 out of 10 varieties of mushrooms found in a typical supermarket.

The increased awareness of medicinal and health benefits of eating mushrooms resulted in imports of more than 90% of fresh and chilled mushrooms demands for fiscal year 2007.  With barely less than 10% of mushroom demand supplied by the single local mushroom producer, there is a huge deficit in the local mushroom supply.  The import of up to 90% of our still growing mushroom demand means that mushrooms have to be flown in daily, contributing to increased carbon dioxide emissions into our atmosphere.  Famous as a Greenhouse Gas (GHG), carbon dioxide is contributing to intense climate change in different parts of the world.  There is a need to increase local mushroom supplies with a methodology that imparts a low carbon footprint.

Blessed with 4 national taps and good water management practices, Singapore does not have to worry about problems of water scarcity till date.  However, up to 1.2 billion continue to face water scarcity each day (WHO, 2009).  What many Singaporeans are unaware of is that we owe virtual water debts to countries from which we import foods high in water content.  In Ecological Economics, the import or export of foods which carry a high water content has been discussed under the terminology of ‘virtual water’.  Comprised up to 80% of water by weight, mushrooms thrive in humid environments and uptakes a high volume of water during growth.  An increase in the import of mushrooms (ie. Virtual water) into Singapore is made at the expense of the availability of drinking water to the poor in developing countries, since precious water used for irrigation purposes yields higher economic benefits.  As a result, developing countries with strong agricultural sectors continue to face simple problems such as shortage of clean drinking water.  An alternative way to meet local mushroom demands without incurring an increasing virtual water debt that translates into drinking water scarcity problems in other countries is required.

Mushroom farming is also a fertilizer intensive form of agriculture as soil nutrients have to be constantly replenished to support the highly intensive form of agriculture required to meet the burgeoning world demand for food.  This is a function of both increasing world population and increased affluence resulting in greater affordability for food.  Fertilizers comprise Nitrogen (N), Phosphorous (P) and Potassium (K) which are vital to the growth of most agricultural crops, however, there has been a decrease in the worldwide supply of NPK (Scheer, 1999).  This signals the need for new environmentally friendly agricultural practices that can ensure a high level of soil fertility while meeting the growing world demand for food and avoid further depletion of global NPK supplies.

Eco Mushroom Cultivation will deliver an unprecedented solution to meet the burgeoning mushroom demand in Singapore.  Environmental sustainability is achieved either through the local practice or through the export of this environmentally friendly methodology of mushroom production.  Eco Mushroom Cultivation promises reduced negative environmental impacts and would impart a low carbon footprint, thus reducing Singapore’s contribution towards Global Warming and Climate Change; reduce our import of virtual water that comes at the expense of water scarcity in other countries; to offer a simple solution to close the global nutrient loop without further depleting global NPK supplies; to inject a revenue-generating step into the conventional waste management of organic outputs from the Singapore beer brewing industry.

Most importantly, Eco Mushroom Cultivation is not just an environmentally sustainable mushroom farming practice.  Based on the principles of sustainability, it is the embodiment of sustainable planning being translated into practice.  A cocktail of creative thinking and small efforts to modify conventional ways of operation Is all it takes to reduce the negative externalities that Singapore imposes on our environment and on people of other countries.  Eco Mushroom Cultivation is proud to demonstrate that sustainability principles can be incorporated into every sector of the economy, so as to inspire other sectors of the economy to think sustainably in (re-)designing the life cycle of their processes.  Eco Mushroom Cultivation also clearly illustrates the inversely proportionate environmental and revenue befefits that can be reaped from just small efforts invested into being a responsible global environmental citizen.

Project Summary

Vertical chutes of high-rise buildings are essential in collecting garbage.  It is dangerous and difficult to clean, inspect and disinfect the internal area of these rubbish chutes.  Regular cleaning or disinfecting of the vertical rubbish chute is a necessity to avoid diseases and foul smell. 

The objectives of this project are to investigate the danger of the existing method to human and the environment, determine the pitfall, and recommend an effective solution in cleaning, inspecting and disinfecting the internal area of the rubbish chute.  One of the possible solutions to do the dangerous tasks is to introduce a robot.