Chapter 10, Problem 10.13P

Interpretation Introduction

(a)

Interpretation:

Derive an expression for the mass generation rate of methane, ${\dot{M}}_{C{H}_4}(t)$ .Without doing any calculations, sketch the shape of a plot of ${\dot{M}}_{C{H}_4}(t)$ versus t from $t=0$ to $t=3y$ and graphically show on the plot the total mass of methane generated in years $1,2$ and $3$. Then derive an expression for $M_{C{H}_4}(t)$, the total mass of methane (tonnes) generated from $t=0$ to a time $t$.

Concept introduction:

$m=V\rho$

Interpretation Introduction

(b)

Interpretation:

A new landfill has a yield potential of $L_0=100SCM\text{}C{H}_4/tonne$ waste and a rate constant $k=0.04y^{-1}$. At the beginning of the first year, $48,000tonnes$ of wastes are deposited in the landfill. Calculate the tonnes of methane generated from this deposit over a three year period.

Interpretation Introduction

(c)

Interpretation:

The methane produced in three years $4.8\times {10}^{4}tonnes$ of waste was calculated using following equation where ${\dot{M}}_{C{H}_4}$ is the first expression derived in part (a).

$M_{C{H}_4}(t=3)={\dot{M}}_{C{H}_4}(t=0)\times 1y+{\dot{M}}_{C{H}_4}(t=1)\times 2y+{\dot{M}}_{C{H}_4}(t=2)\times 3y$

Calculate the value determined with this method and the percentage error in the calculation. Show graphically what the calculated value corresponds to on another sketch of ${\dot{M}}_{C{H}_4}$ vst.

Interpretation Introduction

(d)

Interpretation:

Following amount of waste are deposited in the landfill on January 1 in each of three consecutive years.

	Waste (tonnes)
Year 1	48,000
Year 2	45,000
Year 3	54,000

Calculate the metric tons of CH4 generated through the end of the third year.

Interpretation Introduction

(e)

Interpretation:

Explain in your own words the benefits of reducing the release of methane from landfills and of using the methane as a fuel instead of natural gas.

Interpretation Introduction

(f)

Interpretation:

One way to avoid the environmental hazard of methane generation is to incinerate the waste before it has a chance to decompose. What problems might this alternative process introduce?