Introduce BSFL into the bin and regularly add chopped food waste to ensure a balanced diet that includes moderate amounts of meat and oily items mixed with vegetable scraps and fruit peels. Photos: Soo Tsou Hung
The scale of global food waste is staggering; in 2022, 1.05 billion tonnes ended up in landfills, incinerators or sewers. And over 60% of this waste originated from households, primarily kitchens. Yet, this challenge presents an opportunity.
By repurposing kitchen waste, we can enrich our gardens, promote sustainability and significantly reduce our environmental footprint.
Here are some innovative ways to transform kitchen waste into garden gold, turning the problem into a flourishing backyard solution.
Washed water
We use water for washing rice, fruits, vegetables, boiling pasta and rinsing dishes. While these activities are essential for hygiene and cooking, they also present opportunities for conservation and reuse. One particularly valuable resource is washed rice water (WRW). When rice is washed before cooking, water becomes enriched with nutrients leached from grains. Instead of discarding this nutrient-rich water, it can be repurposed as a natural fertiliser and soil amendment for our plants. To maximise its benefits, consider fermenting the WRW for three days before use. This fermentation process further enhances the nutrient content of WRW and promotes the growth of beneficial microorganisms.
The lifecycle of a black soldier fly (from left): Eggs, prepupa and adult.
Repurposing kitchen waste
Kitchen waste, primarily plant-based scraps such as fruit peels, vegetable trimmings and eggshells, can be transformed into valuable garden resources, such as Effective Microorganisms (EMs) and compost. Both methods avoid the use of meat, dairy and oily items.
EMs are mixtures of beneficial microorganisms that enhance soil health and plant growth. Here is how to create your own:
1. Mix 1 part of kitchen waste with 3-5 parts of water.
2. Add 1-2 tablespoons of brown sugar or molasses per litre of water as the carbon source.
3. Seal the mixture and let it ferment for several days to weeks, stirring occasionally.
4. During fermentation, beneficial microorganisms such as lactic acid bacteria, yeast and photosynthetic bacteria will multiply.
5. Once fermented, dilute the solution (1:100 ratio) with water and use as fertiliser.
An adult black soldier fly.
Composting is a method of recycling organic matter into a rich soil amendment. Follow these steps:
1. Collect plant-based kitchen scraps (shred large pieces first for more rapid decomposition).
2. Create a compost heap or use a bin, tumbler or electric composter.
3. Mix kitchen waste with garden waste (leaves and grass clippings) to achieve a balanced carbon-to-nitrogen ratio.
4. Keep the pile moist but not wet, and turn it regularly for aeration.
5. When the compost is dark, crumbly and earthy-smelling, it is ready for use in the garden.
Both EMs and compost enrich the soil, support plant growth and contribute to more sustainable gardening practices. By implementing these methods, you can significantly reduce household waste while improving your garden’s health.
Black soldier fly larvae
EMs and natural compost avoid meat, dairy and oily items, but black soldier fly larvae (BSFL) offers an efficient and sustainable method for managing these organic wastes. BSFL can consume a wide range of organic materials; however, large bones should be avoided. Follow these steps:
1. Set up a well-ventilated and shaded composting bin with a base layer of dry carbon-rich materials, such as shredded newspapers, and place them in a mesh netting house to prevent adult flies from escaping.
2. Introduce BSFL into the bin and regularly add chopped food waste to ensure a balanced diet that includes moderate amounts of meat and oily items mixed with vegetable scraps and fruit peels. Note: BSFL can be purchased online.
The lifecycle of a black soldier fly includes four stages: egg, larva, pupa and adult fly, with the entire cycle taking approximately 4-6 weeks under optimal conditions (temperatures between 25-35°C). The composting process typically takes a few weeks, during which the larvae decompose food waste into a nutrient-rich compost. This compost is odourless and ideal for enriching soil and supporting plant growth. Additionally, harvested larvae can serve as a high-protein feed for fish and poultry, creating a sustainable and eco- friendly waste management system.
Prepupa stage.
Conclusion
Utilising food waste from the kitchen for home gardening is a practical approach to reducing carbon footprint. By recycling water, creating effective microorganisms and natural compost from kitchen waste, and using BSFL for food waste composting, household waste can be significantly reduced.
These practices not only enrich our soil and promote healthier plant growth but also contribute to a more sustainable and environmentally friendly lifestyle.
Melissa Lok Mei Teng is a Master’s student at the Faculty of Agriculture, Universiti Putra Malaysia. Her Master’s is about developing a rapid soil test kit.
In 2022, she was awarded the Putra Agribio Medal by UPM for her excellent academic, extra-curricular and leadership qualities.
