Why the consumer running sequentially rather than concurrently?

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace ConcurrentMakeTest
{
    class Program
    {
        public static BlockingCollection<string> m_Queue =
             new BlockingCollection<string>();
        public static Object obj = new Object();
        static void Main(string[] args)
        {
            Task producer = Task.Run(() => Producer());
            Task consumer1 = Consumer();
            Task consumer2 = Consumer();
            Task consumer3 = Consumer();
            Task consumer4 = Consumer();

            Task.WaitAll(producer, consumer1, consumer2, consumer3, consumer4);
            Console.WriteLine("-----------------------------------------");
            Console.ReadLine();
        }
        static void Producer()
        {
            try
            {
                for (int i = 0; i <= 10; i++)
                {
                    m_Queue.TryAdd(i.ToString());
                }
            }
            finally
            {
                m_Queue.CompleteAdding();
                Console.WriteLine("There are totally {0} items in the queue.\n", m_Queue.Count);
                Thread.Sleep(500);
            }
        }
        static async Task Consumer()
        {
            try
            {
                while (m_Queue.Count > 0)
                {
                    string x = "";
                    m_Queue.TryTake(out x);
                    await Task.Factory.StartNew(() =>
                    {
                        lock (obj)
                        {
                            PrintItem m = new PrintItem(DateTime.Now);
                            m.RunScript(x);
                        }
                    });
                }

            }
            catch (Exception ex)
            {
                Console.Write("Exception: " + ex.Message + "\r\n" + ex.StackTrace);
            }
        }
    }
}

public class PrintItem
    {
        public PrintItem(DateTime t)
        {
            Console.WriteLine(t);
        }
        internal void RunScript(string item) 
        {
            Console.WriteLine(item);
        }
    }