An improved process for enhancing the plant nutrient value of relatively
low analysis organic waste material (e.g., sewage sludge) involves
treating the waste material with an acid and base in a pipe-cross
reactor. The process more particularly involves mixing the waste material
with water to form a slurry (or initially taking the waste material as a
slurry); pumping the slurry to a pipe-cross reactor for reaction with a
base, acid, and water to form a melt; spraying the melt onto a recycling
bed of fines in a granulator, and flashing off the water contained in the
melt as steam; rolling the melt onto recycled fine particles in a
granulator to form granulated particles; and drying these granulated
particles to form an enhanced plant nutrient value composition (e.g., a
fertilizer or soil conditioner having a greater "NPK" value than the
original relatively low analysis organic waste material). The invention
also includes fertilizers produced according to the improved process,
which fertilizers are of the same size and shape and density of commonly
used fertilizers. The method advantageously utilizes the heat generated
by the exothermic acid-base reaction in the pipe-cross reactor to remove
the approximately 80% water from sludge, thus saving large amounts of
energy normally used in conventional drying or burning methods, while, at
the same time, conserving the intrinsic values of the nutrients and
humates contained in the sludge. In one embodiment, the process includes
a method of disposing of spent acid from a hot dip galvanizing process or
a steel pickling process involving incorporating the spent acid to
maintain the low pH of a venturi scrubber used in the improved process.