Lecture 9b: Composting

Introduction to Composting

  • Greetings and Overview

    • Lecture focus: Introduction to composting in horticulture.

    • Objective: Understand the role of composting in recycling organic matter and its practical applications at home.

    • Reiteration of student learning outcomes.

What is Composting?

  • Nature’s Recycling Method

    • Definition: Composting is a natural process where microorganisms recycle organic material into soil components.

    • Importance: Nature acts as the ultimate recycler, reusing materials and returning nutrients to the soil.

Benefits of Composting

  • Excellent soil amendment:

    • Improves water holding capacity.

    • Increases nutrient retention.

    • Enhances cation exchange capacity, crucial for plant nutrition.

  • Acts as food for soil biology:

    • Explaining the nutrient cycle: waste from one organism becomes food for another.

    • Involvement of various soil organisms in nutrient breakdown.

The Role of Organic Matter

  • Essential for Plant Nutrition

    • Organic matter is the primary nutrient source for plants.

    • Fertilizers should be supplemental, not primary:

    • Analogy: Daily vitamins versus a full diet. Fertilizers are supplements, used only when the soil lacks essential nutrients.

    • Compost usage:

    • Natural soil amendment for top dressing and potting mix.

    • Mulching around plants.

    • Creation of compost tea as a nutrient-rich solution for plants.

Environmental Impact and Significance of Composting

  • Waste Management

    • Composting diverts yard and food waste from landfills.

    • Essential for replacing organic matter in the soil for sustainable ecosystems. Additionally, it reduces greenhouse gas emissions by minimizing methane production in landfills, contributing to a healthier atmosphere.

    • Reduces fire hazards in fire-prone areas by composting organic debris.

    • Decreases reliance on commercial fertilizers by producing home compost.

Methods of Composting

  • Biological Necessities

    • Basic requirements:

    • Biology (microorganisms).

    • Organic matter as food for biology.

  • Composting Methods

    • Static Pile:

    • Basic method: a pile of organic matter composts naturally.

    • Aerated Static Pile:

    • Enhanced by air supply via pipes and blowers.

    • Known for faster composting due to increased oxygen facilitating microbiological activity.

    • Aerated Dynamic Pile:

    • Involves physical mixing, also enhancing aeration.

    • Generates heat through biological activity, reaching 160-165°F to kill pathogens and weed seeds.

    • Biodigesters:

    • Best for high nitrogen, wet material (like food waste).

    • Captures methane produced during anaerobic breakdown for energy usage.

Composting Science and Carbon-Nitrogen Ratios

  • Key Ratios in Composting

    • Ideal ratio: 30 parts carbon (browns) to 1 part nitrogen (greens).

    • Examples:

    • Greens: fresh plant materials, grass clippings.

    • Browns: dried leaves, straw, cardboard.

  • Mechanisms of Nutrient Cycling:

    • Different organic materials contribute uniquely to the composting process, varying in carbon content.

    • Potential mistakes: improper ratios leading to odor problems or insufficient natural composting activity.

    • Greens: kitchen scraps, grass clippings, manure, which are rich in nitrogen and help to accelerate decomposition.

    • Temperature: Maintaining the right temperature is crucial for creating the optimal environment for composting organisms. Browns: dried leaves, straw, and shredded paper, which are high in carbon and provide the necessary balance to promote aeration and prevent moisture loss.

Building and Maintaining a Compost Pile

  • Establishing a Compost Pile

    • Materials preparation: chop/shred organic matter for faster composting.

    • Layering: alternate layers of brown and green materials.

    • Create adequate moisture, controlled airflow, maintain temperature with regular mixing.

    • Use compost starter if needed.

    • Regularly monitor the compost pile to ensure proper decomposition and adjust materials as necessary to maintain balanced carbon-to-nitrogen ratios.

Common Challenges and Considerations

  • Essential Conditions for Composting:

    • Proper moisture level and aeration needed, checking temperatures regularly.

    • Smell as an indicator of compost health: earthy smell is good; sour or rotten signals issues.

What Not to Compost

  • Avoid Contaminants:

    • Invasive weeds, diseased plants, poisonous plants, and animal products (meats, dairy).

    • Synthetic materials, treated wood, and dog/cat manure due to potential pathogens.

Home and Commercial Composting Strategies

  • Home-Level Composting Methods:

    • Static pile or dynamic mixing for efficient compost production.

    • Use of compost tumblers and counter composting kits for ease of management.

  • Vermicomposting:

    • Utilizing worms for break down, achieving nutrient-rich castings.

    • Kits available for home use, easy to set up.

    • Temperature Control: Maintaining an ideal temperature range is crucial for the composting process, as it promotes microbial activity and speeds up decomposition.

Conclusion

  • Encouragement for Composting

    • Explore various methods tailored to lifestyle and space availability.

    • Importance of diverting organic waste to processing facilities as an essential step in sustainable living.